KR101812532B1 - Purification process of nitrous oxide - Google Patents

Abstract

[PROBLEMS] To provide a method for purifying nitrous oxide which can be refined economically even when purifying a large amount of nitrous oxide.
(Solution) A method of introducing nitrous oxide containing at least one of carbon dioxide, nitrogen dioxide, nitrogen monoxide and ammonia as an impurity into an adsorption tower (10) comprising a solid adsorbent containing calcium hydroxide, Nitrogen is contacted to remove impurities from the nitrous oxide to purify the nitrous oxide.

Description

PURIFICATION PROCESS OF NITROUS OXIDE &

The present invention relates to a method for purifying nitrous oxide.

For example, the exhaust gas discharged from a plant for producing adipic acid or nitrous oxide (N ₂ O) contains nitrous oxide, but may contain nitrogen monoxide, carbon dioxide or the like as impurities. Therefore, when the nitrous oxide contained in the exhaust gas is recovered and used, it is necessary to separate and purify nitrogen monoxide, carbon dioxide, etc. from the nitrous oxide.

Patent Documents 1 and 2 disclose a technique for recovering nitrous oxide while purifying nitrous oxide from a mixed gas containing nitrous oxide and nitrogen monoxide using zeolite or activated carbon. In these techniques, there is a process of adsorbing nitrous oxide to zeolite or activated carbon, followed by desorption of nitrous oxide from zeolite or activated carbon.

However, when purifying a large amount of nitrous oxide, it is necessary to use a large amount of an adsorbent such as zeolite or activated carbon, so that there is a problem that the size of the purification facility is large and it is uneconomical.

Japanese Patent Application Laid-Open No. 2004-10391 Japanese Patent Application Laid-Open No. 2003-277027

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for purifying nitrous oxide which can be economically refined even when a large amount of nitrous oxide is refined.

In order to solve the above problems, one form of the present invention is as follows [1] to [8].

[1] A method for purifying nitrous oxide, which comprises introducing nitrous oxide containing at least one of carbon dioxide, nitrogen dioxide, nitrogen monoxide and ammonia as impurities into an adsorption tower having a solid adsorbent containing calcium hydroxide and adding the nitrous oxide to the solid adsorbent containing calcium hydroxide And removing the impurities from the nitrous oxide by contact with the nitrous oxide.

[2] The adsorption column further comprises a solid adsorbent containing Molecular Sieve 3A, wherein the adsorption step comprises bringing the nitrous oxide into contact with the solid adsorbent containing the calcium hydroxide and the solid adsorbent containing the Molecular Sieve 3A A method for purifying nitrous oxide according to [1], comprising the steps of:

[3] The method for purifying nitrous oxide according to [2], wherein the nitrous oxide is contacted with the solid adsorbent containing calcium hydroxide and then further contacted with the solid adsorbent containing the molecular sieve 3A.

[4] The adsorption column according to any one of [1] to [4], further comprising a solid adsorbent containing an alkali metal permanganate, wherein the adsorption step comprises a solid adsorbent containing calcium hydroxide, a solid adsorbent containing the Molecular Sieve 3A, The method for purifying nitrous oxide according to [2] or [3], which comprises contacting the nitrous oxide with a solid-state adsorbent.

[5] The method of producing a catalyst for adsorbing nitrogen oxides according to [4], wherein the nitrous oxide is contacted with the solid adsorbent containing calcium hydroxide and then further contacted with the solid adsorbent containing the alkali metal permanganate and then further contacted with the solid adsorbent containing the molecular sieve 3A Wherein the nitrous oxide is purified.

[6] The method for purifying nitrous oxide according to any one of [1] to [5], wherein the adsorption step is carried out under pressurized conditions.

[7] The method for purifying nitrous oxide according to any one of [1] to [6], further comprising a distillation step of distilling the nitrous oxide.

[8] The method for purifying nitrous oxide according to [7], wherein the nitrous oxide further contains at least one of nitrogen and oxygen as an impurity, and the distillation step includes removing at least one of nitrogen and oxygen.

(Effects of the Invention)

According to the present invention, it is possible to economically purify nitrous oxide even in the case of purifying a large amount of nitrous oxide.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a refining facility used in a method for purifying nitrous oxide according to the first embodiment. FIG.
2 is a schematic view of a refining facility used in a method for purifying nitrous oxide according to the second and third embodiments.
Fig. 3 is a schematic view of a refining facility used in the method for purifying nitrous oxide according to the fourth and fifth embodiments. Fig.
4 is a schematic view of a refining facility used in the method for purifying nitrous oxide according to the sixth embodiment.

As a result of intensive studies, the present inventors have found that a purification method for removing impurities by adsorbing only impurities to an adsorbent without adsorbing nitrous oxide on the adsorbent in the production of purified nitrogen oxides by purifying crude nitrogen oxides containing impurities And has reached the completion of the invention. Hereinafter, one embodiment of the present invention will be described in detail. In the drawings referred to in the following description, the same or equivalent parts are denoted by the same reference numerals.

Carbon dioxide (CO _2), nitrogen dioxide (NO _2), nitrogen monoxide (NO), and ammonia (NH ₃₎ at least a Joa nitrogen oxide gas containing one or as impurities calcium hydroxide of the solid phase containing a (Ca (OH) ₂₎ It is introduced into an adsorption tower having an adsorbent, and a solid oxide adsorbent containing calcium hydroxide is brought into contact with a nitric oxide nitrogen gas, whereby impurities can be removed from the nitric oxide nitrogen gas to produce a nitric oxide nitrogen gas.

Since the purification method including the adsorption process does not adsorb nitrous oxide to the solid adsorbent containing calcium hydroxide but adsorbs only impurities, there is no process of desorbing nitrous oxide from the adsorbent, and even when a large amount of nitrous oxide is refined, It is not necessary to use an adsorbent. Therefore, purification of nitrous oxide can be economically and industrially carried out without increasing the size of the purification facility.

Further, an alkali scrubber method is known as a method of purifying nitrous oxide by passing nitrous oxide through alkaline water to absorb impurities into alkaline water. However, in this method, since nitrous oxide has a high solubility in water, There was a problem that a loss as much as the dissolution occurred. Further, since it is necessary to adjust the pH of the alkaline water absorbent water and to adjust the level of the alkaline water, the alkali scrubber method has a problem that the refining operation is troublesome. However, the purification method using the solid adsorbent containing calcium hydroxide does not cause problems of loss of nitrous oxide or troublesome purification operations.

By this purification method, nitrous oxide of high purity of 99.999% by volume or more in purity can be produced. The produced high-purity nitrous oxide can be used as a raw material for scavenging gas used for anesthetic, for example. It can also be used as a gas for an insulating oxide film in a semiconductor, for example, a semiconductor manufacturing process.

The content of calcium hydroxide in the solid adsorbent containing calcium hydroxide may be 70 mass% or more. Further, the solid adsorbent containing calcium hydroxide may contain an alkali metal salt together with calcium hydroxide. The kind of the alkali metal salt is not particularly limited, and examples thereof include sodium hydroxide (NaOH) and potassium hydroxide (KOH). The content of the alkali metal salt in the solid adsorbent containing calcium hydroxide may be 1% by mass or more and 5% by mass or less. In addition, the solid adsorbent containing calcium hydroxide may contain water together with calcium hydroxide. The content of water in the solid adsorbent containing calcium hydroxide may be 12 mass% or more and 25 mass% or less.

An example of a solid adsorbent containing calcium hydroxide is soda lime. Soda lime contains, for example, 80% by weight of calcium hydroxide, 5% by weight of sodium hydroxide and 15% by weight of water. The sodalime preferably has a particle size of not more than 5 mm, particularly not less than 1.5 mm and not more than 3.5 mm. Specific examples include Soda lime Yabase 1 (trade name) available from Yabase Corporation, and Wako Lime (registered trademark) available from Wako Pure Chemical Industries, Ltd.

The adsorption tower may be loaded with a solid adsorbent containing calcium hydroxide and a solid adsorbent containing Molecular Sieve 3A. A specific example of the solid adsorbent containing Molecular Sieve 3A is Molecular Sieve 3A (MS-3A) manufactured by Union Showa K.K.

The adsorption column may also be loaded with a solid adsorbent containing calcium hydroxide and a solid adsorbent containing a molecular sieve 3A, together with a solid adsorbent containing alkali metal permanganate.

The solid adsorbent containing permanganic acid alkali metal salt may contain 10 mass% or more of alkali metal permanganate. In addition, water may be contained in an amount of 10% by mass or more. The kind of alkali metal permanganate alkali metal is not particularly limited, and examples thereof include lithium (Li), sodium (Na), potassium (K) and rubidium (Rb).

As a specific example of the solid adsorbent containing an alkali metal permanganate, Purafil SP (registered trademark) of Purafusa Co., Ltd. can be mentioned. Purafil SP contains 15 mass% of permanganate sodium supported on a carrier composed of 55 mass% of active alumina and 30 mass% of water.

[First Embodiment]

Hereinafter, a nitrogen oxynitride gas containing carbon dioxide as an impurity is introduced into an adsorption tower having sodalime in solid form, and nitrogen oxide gas is contacted with solid soda lime to remove carbon dioxide from the nitric oxide gas, An example of producing a gas will be described.

When soda lime is used as a solid adsorbent containing calcium hydroxide, carbon dioxide is adsorbed by the reaction shown in the following reaction formula.

H ₂ O + CO _{2 -} > H ₂ CO ₃

H ₂ CO _{3 +} Ca (OH) _{2 -} > CaCO _{3 +} 2H ₂ O

Also, in the presence of sodium hydroxide, carbon dioxide is adsorbed by the reaction shown in the following reaction formula.

H ₂ O + CO _{2 -} > H ₂ CO ₃

H ₂ CO ₃ + ₂ NaOH → Na ₂ CO ₃ + 2H ₂ O

_{Na 2 CO 3 + Ca (OH} ) 2 → CaCO 3 + 2NaOH

Carbon dioxide is formed by dissolving carbon dioxide in water contained in soda lime, and carbonic acid is sequentially neutralized by sodium hydroxide or calcium hydroxide. Therefore, the soda lime having a high water content has a high ability to remove carbon dioxide.

The content of carbon dioxide contained as impurities in the nitrous oxide is preferably less than 1000 ppm by volume and more preferably less than 300 ppm by volume in order to make both the life of the solid adsorbent containing calcium hydroxide and the production efficiency of nitrate nitrogen oxide advantageous. When the content of carbon dioxide is at least 1000 ppm by volume, it may be necessary to increase the amount of the solid adsorbent containing calcium hydroxide to the adsorption tower.

The adsorption of carbon dioxide is preferably carried out at a temperature of less than 50 DEG C, more preferably at a temperature of 5 DEG C or more and 30 DEG C or less. If the temperature is less than 50 캜, the dehydration of soda lime is not accelerated so that the life of the soda lime becomes long.

In addition, the linear velocity (LV) of nitrous oxide at the time of adsorption of carbon dioxide is preferably 0.3 m / min or less, more preferably 0.15 m / min or more and 0.26 m / min or less. Further, the space velocity (SV) of the nitrous oxide during the adsorption of carbon dioxide is preferably 93 or less, more preferably 46 or more and 79 or less. The space velocity is the air flow rate per unit time of the gas passing through the adsorbent divided by the volume of the adsorbent.

The adsorption of carbon dioxide is preferably carried out under pressurized conditions, more preferably under pressurization conditions of 3 MPa or more, and more preferably under pressurization conditions of 3.5 MPa or more and 6 MPa or less. The adsorption of carbon dioxide under the pressurized condition is advantageous in terms of the adsorption efficiency and the lifetime of the adsorbent because it is possible to increase the residence time of the nitrogen oxynitride in the adsorption tower (that is, to reduce the linear velocity and space velocity) .

Next, a description will be given of a method for purifying nitric oxide under a pressurizing condition using the purification equipment shown in Fig. The refining facility of Fig. 1 is equipped with an adsorption tower 10 loaded with soda lime. When nitrogen oxynitride containing carbon dioxide as an impurity is introduced into the adsorption tower 10 under pressure, carbon dioxide in the nitrogen oxynitride is adsorbed by soda lime. Nitric oxide nitrogen having a purity of, for example, 99.999% by volume or more is adsorbed to the adsorption tower 10 .

[Second embodiment]

Hereinafter, a nitrogen oxynitride gas containing ammonia as an impurity is introduced into an adsorption tower having sodalime and molecular sieve 3A, and nitrogen oxynitride gas is brought into contact with sodalime and molecular sieve 3A, and ammonia Is removed to produce a nitrous oxide gas.

The content of ammonia contained as an impurity in the nitrous oxide is preferably less than 25 ppm by volume and more preferably less than 1 ppm by volume in order to make both the life of the adsorbent and the production efficiency of nitrate nitrogen oxide advantageous. When the content of ammonia is 25 ppm by volume or more, it may be necessary to increase the adsorption amount of the adsorbent to the adsorption tower.

Also, the ratio of sodalime and molecular sieve 3A is preferably in the range of 1: 1 to 1: 5 (mass ratio) of sodalime: molecular sieve 3A, depending on the composition of the oxidized nitrogen oxide to be treated.

It is also preferable that the nitrogen oxynitride containing ammonia as an impurity is further brought into contact with the molecular sieve 3A after contacting the sodalime.

The adsorption of ammonia is preferably performed at a temperature of less than 50 DEG C, and more preferably at a temperature of 5 DEG C or more and 30 DEG C or less. If the temperature is less than 50 캜, the dehydration of soda lime is not accelerated so that the life of the soda lime becomes long.

In addition, the linear velocity of nitrous oxide during the adsorption of ammonia is preferably 0.3 m / min or less, more preferably 0.15 m / min or more and 0.26 m / min or less. Further, the space velocity of nitrous oxide during the adsorption of ammonia is preferably 93 or less, more preferably 46 or more and 79 or less.

The adsorption of ammonia is preferably carried out under pressurizing conditions, more preferably under pressurizing conditions of 3 MPa or more, and more preferably under pressurization conditions of 3.5 MPa or more and 6 MPa or less. The adsorption of ammonia under the pressurized condition is advantageous in terms of the adsorption efficiency and the lifetime of the adsorbent because it is possible to increase the residence time of the nitrogen oxynitride in the adsorption tower (that is, the linear velocity and the space velocity can be reduced) .

Next, a description will be given of a method for purifying nitric oxide under a pressurizing condition using the purification equipment shown in Fig. 2 includes an adsorption column 10 loaded with soda lime and an adsorption column 20 loaded with a molecular sieve 3A. Nitrogen oxynitride containing ammonia as an impurity is introduced into the adsorption tower 10 in a pressurized state and then introduced into the adsorption tower 20 to purify nitrate nitrogen oxide having a purity of, for example, 99.999% by volume or more from the adsorption tower 20 do. Water may be released from the soda lime. However, since water is adsorbed by the molecular sieve 3A, high purity nitrous oxide is discharged from the adsorption tower 20. [

[Third embodiment]

Hereinafter, a nitrogen oxynitride gas containing carbon dioxide, nitrogen dioxide, and nitrogen monoxide as impurities is introduced into an adsorption tower having sodalime and molecular sieve 3A, and soda lime and molecular sieve 3A are contacted with a nitrogen oxynitride gas An example will be described in which carbon dioxide, nitrogen dioxide, and nitrogen monoxide are removed from the crude nitric oxide gas to produce a purified nitric oxide gas.

Carbon dioxide is removed from the nitrogen oxynitride gas by soda lime as in the first embodiment. On the other hand, nitrogen dioxide and nitrogen monoxide are adsorbed on soda lime by the reaction shown in the following reaction formula and removed from the crude nitric oxide gas.

3NO ₂ + H ₂ O? 2HNO ₃ + NO

_{Ca (OH) 2 + 2HNO 3} → Ca (NO 3) 2 + 2H 2 O

_{Ca (NO 3) 2 + 2NO} → Ca (NO 2) 2 + 2NO 2

Nitric acid is produced by dissolving nitrogen dioxide in water contained in soda lime, and calcium nitrate is reacted with calcium hydroxide to produce calcium nitrate. Nitrogen monoxide is oxidized to nitrogen dioxide by calcium nitrate, and calcium nitrate becomes calcium nitrite.

The content of carbon dioxide contained in the crude nitric oxide as an impurity is preferably less than 1000 ppm by volume, more preferably less than 300 ppm by volume, as described above.

The content of nitrogen dioxide contained as impurities in the crude nitric oxide is preferably less than 30 ppm by volume and more preferably less than 1 ppm by volume in order to make both the life of soda lime and the production efficiency of nitrate nitrogen oxide advantageous. When the content of nitrogen dioxide is 30 ppm by volume or more, it may be necessary to increase the total amount of soda lime to the adsorption tower.

The content of nitrogen monoxide contained as impurities in the crude nitric oxide is preferably less than 10 ppm by volume and more preferably less than 1 ppm by volume in order to favor both the life of soda lime and the production efficiency of nitrate nitrogen oxide. When the content of nitrogen monoxide is 10 ppm by volume or more, it may be necessary to increase the total amount of soda lime to the adsorption tower.

Also, the ratio of sodalime and molecular sieve 3A is preferably in the range of 1: 1 to 1: 5 (mass ratio) of sodalime: molecular sieve 3A, depending on the composition of the oxidized nitrogen oxide to be treated.

It is also preferable that the nitrogen oxynitride containing carbon dioxide, nitrogen dioxide, and nitrogen monoxide as impurities is further brought into contact with the molecular sieve 3A after contacting with soda lime.

The adsorption of carbon dioxide, nitrogen dioxide, and nitrogen monoxide is preferably carried out at a temperature of less than 50 ° C, more preferably at a temperature of 5 ° C or more and 30 ° C or less. If the temperature is less than 50 캜, the dehydration of soda lime is not accelerated so that the life of the soda lime becomes long.

In addition, the linear velocity of nitrous oxide during adsorption of carbon dioxide, nitrogen dioxide, and nitrogen monoxide is preferably 0.3 m / min or less, more preferably 0.15 m / min or more and 0.26 m / min or less. In addition, the space velocity of nitrous oxide during adsorption of carbon dioxide, nitrogen dioxide, and nitrogen monoxide is preferably 93 or less, more preferably 46 or more and 79 or less.

The adsorption of carbon dioxide, nitrogen dioxide and nitrogen monoxide is preferably carried out under pressurizing conditions, more preferably under pressurization conditions of 3 MPa or more, and more preferably under pressurization conditions of 3.5 MPa or more and 6 MPa or less. The adsorption of carbon dioxide, nitrogen dioxide, and nitrogen monoxide under the pressurized condition can increase the time during which the nitrogen oxynitride stays in the adsorption tower (that is, the linear velocity and the space velocity can be reduced) . ≪ / RTI >

Next, a description will be given of a method for purifying nitric oxide nitrogen under pressurized condition using the purification equipment shown in Fig. When crude nitric oxide containing carbon dioxide, nitrogen dioxide, and nitrogen monoxide as impurities is introduced into the adsorption tower 10 under a pressurized condition, nitrate nitrogen oxide having a purity of, for example, 99.999% by volume or more is discharged from the adsorption tower 20. Water may be released from the soda lime. However, since water is adsorbed by the molecular sieve 3A, high purity nitrous oxide is discharged from the adsorption tower 20. [

[Fourth Embodiment]

Hereinafter, a nitrogen oxynitride gas containing nitrogen monoxide and ammonia as an impurity is introduced into an adsorption tower having sodalime, a solid-phase adsorbent containing an alkali metal permanganate and a molecular sieve 3A, and a soda lime and an alkali metal permanganate And a method for producing nitrogen oxide and nitrous oxide by contacting nitrogen oxynitride gas with Molecular Sieve 3A and removing nitrogen monoxide and ammonia from the oxidized nitrogen gas will be described.

The nitrogen monoxide is adsorbed to the alkali metal permanganate by the reaction shown in the following reaction formula and is removed from the nitrogen oxynitride gas. The reaction formula when the alkali metal permanganate is sodium permanganate is shown below.

_{3NO + 2NaMnO 4 + H 2 O} → 3NO 2 + 2MnO 2 + 2NaOH

3NO ₂ + NaMnO ₄ + 2NaOH 3NaNO ₃ + MnO ₂ + H ₂ O

By oxidation with sodium permanganate intervening in water, nitrogen monoxide becomes nitrogen dioxide. Then, it is finally fixed as sodium nitrate by the reaction of nitrogen dioxide, sodium permanganate and sodium hydroxide. Since water is required in the reaction of the shear, the ability to remove nitrogen monoxide is higher when the solid adsorbent containing alkali metal permanganate contains a large amount of water.

The content of nitrogen monoxide contained as impurities in the crude nitric oxide is preferably less than 10 ppm by volume and more preferably less than 1 ppm by volume in order to make both the life of the adsorbent and the production efficiency of nitrate nitrogen oxide favorable Do.

In addition, the content of ammonia contained as impurities in the crude nitric oxide is preferably less than 25 ppm by volume, and it is preferable that the content of ammonia is less than 1 part by volume in order to advantage both of the life of the adsorbent and the production efficiency of nitrate nitrogen oxide More preferable.

The ratio of sodalime and alkali metal permanganate to alkali metal permanganate is preferably in the range of 1: 9 to 9: 5 (by mass ratio), based on the composition of nitrogen oxynitride to be treated, but sodalum: alkali metal permanganate. The total amount of sodalime and permanganic acid alkali metal salt and the moleculous sieve 3A is preferably in the range of 1: 9 to 9: 5, based on the total amount of sodalime and alkali metal permanganate: Molecular Sieve 3A, (Mass ratio).

Further, the nitrogen oxynitride containing nitrogen monoxide and ammonia as an impurity is preferably brought into contact with sodalime and then further contacted with a solid-state adsorbent containing an alkali metal permanganate, and further, after contact with soda lime, an alkali metal permanganate It is more preferable to contact the solid adsorbent to be further contacted with the molecular sieve 3A.

The adsorption of nitrogen monoxide and ammonia is preferably carried out at a temperature of less than 50 DEG C, more preferably at a temperature of 5 DEG C or more and 30 DEG C or less. When the temperature is less than 50 캜, the dehydration of the solid adsorbent containing soda lime or alkali metal permanganate hardly accelerates, and the lifetime of the solid adsorbent containing soda lime or alkali metal permanganate becomes long.

In addition, the linear velocity of nitrous oxide during adsorption of nitrogen monoxide and ammonia is preferably 0.3 m / min or less, more preferably 0.15 m / min or more and 0.26 m / min or less. Further, the space velocity of nitrous oxide during adsorption of nitrogen monoxide and ammonia is preferably 93 or less, more preferably 46 or more and 79 or less.

The adsorption of nitrogen monoxide and ammonia is preferably carried out under pressurizing conditions, more preferably under pressurizing conditions of 3 MPa or more, and more preferably under pressurization conditions of 3.5 MPa or more and 6 MPa or less. Since the adsorption of nitrogen monoxide and ammonia under the pressurized condition can increase the residence time of the nitrogen oxynitride in the adsorption tower (that is, the linear velocity and the space velocity can be reduced), the adsorption efficiency and the life of the adsorbent .

Next, a method of purifying nitric oxide nitrogen under a pressurizing condition using the purification equipment shown in Fig. 3 will be described. 3 includes an adsorption tower 10 in which a solid adsorbent containing soda lime and alkali metal permanganate is loaded, and an adsorption tower 20 in which a molecular sieve 3A is loaded. The adsorption tower 10 is divided into two areas by a partition wall capable of ventilation. Soda lime is placed in the region 10A on the upstream side, and a solid adsorbent containing alkali metal permanganate is loaded in the region 10B on the downstream side have.

When the crude nitric oxide containing nitrogen monoxide and ammonia as impurities is introduced into the adsorption tower 10 in a pressurized state, the nitrogen oxynitride discharged from the adsorption tower 10 is introduced into the adsorption tower 20, and as a result, 99.999% by volume or more of nitrate nitrogen oxide is discharged from the adsorption tower 20.

[Fifth Embodiment]

Hereinafter, a nitrogen oxynitride gas containing carbon dioxide and nitrogen dioxide as impurities is introduced into an adsorption tower having sodalime, a solid-phase adsorbent containing an alkali metal permanganate and a molecular sieve 3A, and a soda lime, an alkali metal permanganate The solid-state adsorbent, and the molecular sieve 3A are brought into contact with the nitric oxide gas to remove carbon dioxide and nitrogen dioxide from the nitric oxide nitrogen gas to prepare a purified nitric oxide gas.

The content of carbon dioxide contained in the crude nitric oxide as an impurity is preferably less than 1000 ppm by volume, more preferably less than 300 ppm by volume, as described above. The content of nitrogen dioxide contained as impurities in the crude nitric oxide is preferably less than 30 volume ppm, more preferably less than 1 volume ppm, as described above.

The ratio of sodalime to the alkali metal permanganate and the ratio of the sum of sodalime and alkali metal permanganate to the molecular sieve 3A are the same as in the fourth embodiment.

In addition, the preferred order of bringing the nitrogen oxynitride containing carbon dioxide and nitrogen dioxide as impurities into contact with each adsorbent is the same as in the fourth embodiment.

The adsorption of carbon dioxide and nitrogen dioxide is preferably carried out at a temperature of less than 50 ° C, more preferably at a temperature of 5 ° C or more and 30 ° C or less. When the temperature is less than 50 캜, the dehydration of the solid adsorbent containing soda lime or alkali metal permanganate hardly accelerates, and the lifetime of the solid adsorbent containing soda lime or alkali metal permanganate becomes long.

In addition, the linear velocity of nitrous oxide during adsorption of carbon dioxide and nitrogen dioxide is preferably 0.3 m / min or less, more preferably 0.15 m / min or more and 0.26 m / min or less. In addition, the space velocity of nitrous oxide during adsorption of carbon dioxide and nitrogen dioxide is preferably 93 or less, and more preferably 46 or more and 79 or less.

The adsorption of carbon dioxide and nitrogen dioxide is preferably carried out under pressurized conditions, more preferably under pressurized conditions of 3 MPa or more, and more preferably under pressurized conditions of 3.5 MPa or more and 6 MPa or less. Since the adsorption of carbon dioxide and nitrogen dioxide under the pressurized condition can increase the time during which nitrogen oxynitride stays in the adsorption tower (that is, the linear velocity and space velocity can be made small), the adsorption efficiency and the adsorbent life .

Next, a description will be given of a method for purifying nitric oxide under a pressurizing condition using the purification equipment shown in Fig. When nitrogen oxynitride containing carbon dioxide and nitrogen dioxide as impurities is introduced into the adsorption tower 10 under a pressurized condition, nitrogen pentaoxide at a purity of, for example, 99.999% by volume or more is discharged from the adsorption tower 20. Water may be released from the soda lime. However, since water is adsorbed by the molecular sieve 3A, high purity nitrous oxide is discharged from the adsorption tower 20. [

[Sixth Embodiment]

A nitrogen oxide gas containing carbon dioxide, nitrogen dioxide, nitrogen (N ₂ ), and oxygen (O ₂ ) as an impurity is introduced into a solid adsorbent containing soda lime, an alkali metal permanganate and a molybdenum sheath 3A , A solid adsorbent containing soda lime and an alkali metal permanganate, and a molecular sieve 3A contacting a molecular oxygen nitrogen gas to the molecular sieve 3A to remove carbon dioxide and nitrogen dioxide from the oxidized nitrogen gas. Further, in the distillation column, An example of producing a nitrous oxide gas by removing low boiling point impurities will be described.

The nitrogen oxynitride may contain carbon dioxide, nitrogen dioxide, nitrogen monoxide, ammonia as well as other impurities. Other impurities include low boiling point impurities such as methane, hydrogen, nitrogen, oxygen, and helium. These low boiling point impurities can be removed by distillation. Therefore, the distillation step may be performed before or after the adsorption step with the adsorption towers 10 and 20 as described above to remove the low boiling point impurities.

An example of a facility for purifying nitrous oxide capable of performing the distillation step is shown in Fig. 4 includes a distillation column 30 together with adsorption towers 10 and 20 (the same as the purification facilities of the second to fifth embodiments). A condenser (not shown in the figure) and a low boiling point component discharge pipe 31 are provided at the top of the distillation tower 30 and a high purity nitrous oxide discharge pipe 32 is provided at the bottom of the distillation tower 30.

Nitrogen oxides, such as carbon dioxide, nitrogen dioxide, nitrogen monoxide and ammonia, which are removed by the adsorption columns 10 and 20 and contain low boiling point impurities such as methane, hydrogen, nitrogen, oxygen and helium, As shown in Fig. The nitrous oxide in the column top of the distillation column 30 is cooled by the condenser and liquefied, and a part thereof is discharged through the low boiling point component discharge pipe 31. A part of the nitrous oxide is discharged through the low boiling point component discharge pipe 31 to remove low boiling point impurities such as methane, hydrogen, oxygen, nitrogen, helium and the like which are low boiling point components, so that nitrous oxide is refined and becomes high purity nitrous oxide. The high purity nitrous oxide is discharged from the bottom of the column of the distillation column 30 through the high-purity nitrous oxide discharge pipe 32.

The height of the distillation tower 30 is set on the basis of the concentration of the low boiling point impurities in the nitrous oxide and is preferably 3 m or more and 20 m or less, more preferably 5 m or more and 10 m or less. As the height of the distillation tower 30 is designed to be larger, the component separation performance is improved. On the other hand, if the height of the distillation tower 30 is set too large, the cost of the apparatus increases greatly. It is preferable to design the height of the distillation tower 30 to 5 m or more when the concentration of the low boiling point impurity in the nitrite nitrogen is measured and, for example, when the concentration of oxygen or nitrogen is high at 500 ppm or more. When the concentration of oxygen or nitrogen, which is a low boiling point impurity in the nitrous acid, is about 500 vol. Ppm, the height of the distillation tower 30 may be increased up to 20 m or less. In the case of ppm, the height of the distillation tower 30 is 3 m or more. The distillation operation conditions include, for example, a temperature of 5 ° C or more and 25 ° C or less, and a pressure of 3.5 MPa or more and 4.5 MPa or less.

It should be noted that the above-described embodiments illustrate examples of the present invention, and the present invention is not limited to the above-described embodiments. It is to be noted that various modifications or improvements may be added to the embodiments, and modifications or improvements may be included in the present invention.

Since the calcium hydroxide and the alkali metal permanganate used in the first to sixth embodiments are consumed when adsorbing the impurities, the solid adsorbent containing the calcium hydroxide and the alkali metal permanganate are subjected to the removal of the impurities once You can not use it repeatedly. On the other hand, since the molecular sieve 3A can be regenerated, the solid adsorbent containing the molecular sieve 3A can be repeatedly used for removal of impurities by performing a regeneration treatment for desorbing water or the like adsorbed.

(Example)

Hereinafter, the present invention will be described in more detail by way of examples.

[Example 1: Removal of carbon dioxide]

The crude nitric oxide containing carbon dioxide was purified as an impurity under normal temperature and normal pressure conditions by using a purification apparatus almost the same as in Fig. The content of carbon dioxide in the nitrogen oxynitride was 680 volume ppm and was prepared by mixing carbon dioxide and nitrous oxide using a mass flow meter.

The dimensions of the adsorption column are 6 cm in outer diameter, 4.88 cm in inner diameter, and 5 cm in height, and soda lime is loaded. Test No. The adsorption tower of No. 1 was loaded with soda lime (Soda lime Yabase 213, water content 3% by mass, product of Yabase Corporation) at room temperature by N ₂ purging and dried, and the amount of the bed was 73.48 g. Also, In the adsorption tower of No. 2, soda lime (Soda lime Yabase 213, moisture content: 3% by mass, product of Yabase Corporation) was loaded as it was without drying treatment, and the total amount of charge was 76.27 g. In addition, 3 was loaded with sodium soda lime (Soda lime Yabase 2 manufactured by YABASE CHEMICAL INDUSTRIAL CO., LTD., Water content: 15 mass%) as it is without drying treatment, and the total amount of the soda lime was set to 75.52 g.

The introduction conditions of the nitrogen oxynitride into the adsorption column were set to a linear velocity of 0.14 m / min and a space velocity of 163. The nitrous oxide discharged from the adsorption tower was analyzed by FT-IR (Fourier transform infrared spectroscopic analyzer), and the experiment was terminated when the content of carbon dioxide in the nitrous oxide reached 1 ppm by volume or more due to the breakage of soda lime as the adsorbent .

As a result, when the content of carbon dioxide, which was less than 1 ppm by volume, was 1 ppm by volume or more, In the case of the adsorption tower No. 1, after about 18 hours from the start of adsorption, In the case of the adsorption tower No. 2, after about 48 hours, 3 adsorption towers after about 91 hours. From these results, it was found that by using soda lime as the adsorbent, carbon dioxide contained in the nitrous oxide can be effectively removed.

[Example 2: Removal of carbon dioxide]

Purification of crude nitric oxide containing carbon dioxide as an impurity was carried out under a pressurizing condition by using the same refining equipment as in Fig. The adsorption temperature was set at room temperature or 50 ° C. The content of carbon dioxide in the nitrogen oxynitride was 800 ppm by volume and was prepared by mixing carbon dioxide and nitrous oxide using a mass flow meter.

The temperature of the bomb charged with the nitrogen oxynitride was set to 7 캜 by a refrigerant circulating apparatus not shown in the figure, and a nitrogen oxynitride gas having a pressure of 3.7 MPa was generated from the bomb to be introduced into the adsorption tower loaded with soda lime. The dimensions of the adsorption tower are 1.9 cm (3/4 inch) in outer diameter, 1.55 cm in inner diameter, 20 cm in height or 100 cm in height.

Test No. The adsorption tower of 11 was 100 cm high and was loaded as it is without drying treatment, and 165 g (100 cm in bed height) of the standard product soda lime (Soda lime Yabase 2 manufactured by Yabase Kogyo Co., Ltd., moisture content: 15 mass% did. Also, The adsorption tower of No. 12 was 20 cm in height, and was loaded as it is without drying treatment, and 31.7 g (20 cm in height) of the standard product soda lime (Soda lime Yabase 2 manufactured by Yabase Kogyo Co., Ltd., moisture content: 15 mass% .

The introduction conditions of the nitrogen oxynitride into the adsorption column were set at a linear velocity of 0.25 m / min and a space velocity of 15 when the temperature condition was normal temperature and 75 when the temperature condition was 50 ° C. The nitrous oxide discharged from the adsorption tower was analyzed by FT-IR, and the experiment was terminated when the content of carbon dioxide in the nitrous oxide reached 1 ppm by volume or more due to the break-up of soda lime as an adsorbent.

As a result, it was confirmed that the content of carbon dioxide, which was less than 1 ppm by volume, was 1 ppm by volume or more. When the temperature condition was normal temperature using the adsorption tower No. 11, after about 443 hours from the start of adsorption, 12 when the adsorption tower was used and the temperature condition was 50 캜. From these results, it was found that by using soda lime as the adsorbent, carbon dioxide contained in the nitrous oxide can be effectively removed.

[Example 3: Removal of ammonia]

Purification of crude nitric oxide containing ammonia as an impurity was carried out under a pressurizing condition by using the same purification apparatus as in Fig. The adsorption temperature was set at 60 占 폚. The content of ammonia in the crude nitric oxide was 30 ppm by volume and was prepared by mixing ammonia and nitrous oxide with a mass flow meter.

The liquefied gas supplied from the bomb charged with nitrogen oxynitride was vaporized by passing through a piping heated to 80 DEG C by an oil bath not shown in the figure and the temperature was raised to 60 DEG C by a heater not shown in the figure, Of nitrogen oxide gas. Then, the nitrogen oxynitride gas was introduced into an adsorption tower loaded with soda lime (Soda lime Yabase 1 manufactured by YABASE CHEMICAL INDUSTRIAL CO., LTD., A total amount of 32.91 g), and then molecular sieve 3A (manufactured by Union Showa Co., Ltd.) Product Molecular Sieve 3A, full charge 29.25 g) was introduced into the loaded adsorption column. The dimensions of the two adsorption columns are 1.9 cm (3/4 inch) in outer diameter, 1.55 cm in inner diameter, and 20 cm in height.

The conditions of introduction of nitrogen oxynitride into the adsorption column were set at a linear velocity of 0.25 m / min and a space velocity of 75. The nitrous oxide discharged from the adsorption tower loaded with Molecular Sieve 3A was analyzed by FT-IR, and the experiment was terminated when the content of ammonia in the nitrous oxide reached 1 ppm or more by breakthrough. As a result, it was found that the content of ammonia, which was less than 1 ppm by volume, exceeded 1 ppm by volume after about 30 hours from the start of adsorption. From this result, it was found that ammonia contained in the nitrous oxide can be effectively removed by combining sodalime and Molecular Sieve 3A as the adsorbent.

After the purification of nitrous oxide was completed, the used soda lime in the adsorption tower was replaced with 33.73 g of new soda lime. Further, the used molecular sieve 3A was recovered from the adsorption tower, regenerated, and then returned to the adsorption tower. The regeneration treatment is performed under a nitrogen stream. The conditions are temperature 200 ° C, time 15 hours, linear velocity of nitrogen stream 2.3 m / min, space velocity 700. It was confirmed that almost all the same results were obtained when the nitrous oxide was purified using the adsorption tower in which the adsorbent was replaced as described above.

[Example 4: Removal of carbon dioxide, nitrogen dioxide, and nitrogen monoxide]

Purification of crude nitric oxide containing carbon dioxide, nitrogen dioxide, and nitrogen monoxide as impurities was carried out under a pressurizing condition by using the same refining equipment as in Fig. The adsorption temperature was set at 60 占 폚.

The content of carbon dioxide in the nitrogen oxynitride was 500 ppm by volume, the content of nitrogen dioxide was 30 ppm by volume, and the content of nitrogen monoxide was 10 ppm by volume, and carbon dioxide, nitrogen dioxide, nitrogen monoxide and nitrogen oxynitride were mixed using a mass flow meter .

The liquefied gas supplied from the bomb charged with nitrogen oxynitride was vaporized by passing through a piping heated to 80 DEG C by an oil bath not shown in the figure and the temperature was raised to 60 DEG C by a heater not shown in the figure, Of nitrogen oxide gas. Then, the nitrogen oxynitride gas was introduced into an adsorption tower loaded with soda lime (Soda lime Yabase 1 manufactured by YABASE CHEMICAL INDUSTRIAL CO., LTD., Total amount 33.63 g, bed height 20 cm), and then Molecular Sieve 3A Molecular Sieve 3A manufactured by Kabushiki Kaisha, total length 29.77 g, bed height 20 cm) was introduced into the loaded adsorption column. The dimensions of the two adsorption columns are 1.9 cm (3/4 inch) in outer diameter, 1.55 cm in inner diameter, and 20 cm in height.

The conditions of introduction of nitrogen oxynitride into the adsorption column were set at a linear velocity of 0.25 m / min and a space velocity of 75. Nitrous oxide discharged from the adsorption column loaded with Molecular Sieve 3A was analyzed by FT-IR, and contents of carbon dioxide, nitrogen dioxide, nitrogen monoxide and water in the nitrous oxide were measured. As a result, it was found that the content of carbon dioxide, which was less than 1 ppm by volume, exceeded 1 ppm by volume due to breakage, after about 78 hours from the start of adsorption.

It was also found that the content of nitrogen monoxide, which was less than 1 ppm by volume, became more than 1 ppm by adsorption of soda lime, which is an adsorbent, after about 29 hours and the content of water which was less than 1 ppm by volume was destroyed by Molecular sieve 3A It was after about 87 hours that it became more than 1 ppm by volume. Nitrogen dioxide did not break through. From this result, it can be seen that the carbon dioxide, nitrogen dioxide, and nitrogen monoxide contained in the nitrous oxide can be effectively removed and the water released from the soda lime can be effectively removed by combining the sodalime and the Molecular Sieve 3A as the adsorbent there was.

After the completion of purification of nitrous oxide, the used soda lime in the adsorption column was replaced with new soda lime, the used molecular sieve 3A was recovered and regeneration treatment was carried out in the same manner as in Example 3, , It was confirmed that almost the same results were obtained.

[Example 5: Removal of ammonia and nitrogen monoxide]

Using the same purification equipment as in Fig. 3, purification of crude nitric oxide containing ammonia and nitrogen monoxide as impurities was carried out under pressure conditions. The adsorption temperature was set at 60 占 폚. The content of ammonia in the nitrogen oxynitride was 30 ppm by volume and the content of nitrogen monoxide was 10 ppm by volume and was prepared by mixing ammonia, nitrogen monoxide and nitrous oxide with a mass flow meter.

The liquefied gas supplied from the bomb charged with nitrogen oxynitride was vaporized by passing through a piping heated to 80 DEG C by an oil bath not shown in the figure and the temperature was raised to 60 DEG C by a heater not shown in the figure, Of nitrogen oxide gas. Then, a sodalime (Soda Lime Yabase 1 manufactured by YABASE CHEMICAL INDUSTRIAL CO., LTD., A total amount of 30 g and a bed height of 18 cm) was loaded in the upstream region, and a solid adsorbent containing an alkali metal permanganate in the downstream region , And the molecular sieve 3A (manufactured by Union Showa Kabushiki Kaisha Molecular Sieve 3A, manufactured by Union Showa Co., Ltd.) was introduced into the adsorption tower loaded with the polyolefin resin (Purafil SP (registered trademark), 3.7 g, Total weight 30 g, bed height 20 cm) was introduced into the loaded adsorption column. The dimensions of the two adsorption columns are 1.9 cm (3/4 inch) in outer diameter, 1.55 cm in inner diameter, and 20 cm in height.

The conditions of introduction of nitrogen oxynitride into the adsorption column were set at a linear velocity of 0.25 m / min and a space velocity of 75. The nitrous oxide discharged from the adsorption column loaded with Molecular Sieve 3A was analyzed by FT-IR and the contents of ammonia and nitrogen monoxide in the nitrous oxide were measured. As a result, the content of ammonia, which was less than 1 ppm by volume, became 1 ppm or more by breakthrough was about 42 hours after the start of adsorption, and the adsorption capacity of ammonia increased as compared with Example 3.

The content of nitrogen monoxide, which was less than 1 ppm by volume, was more than 1 ppm by volume due to the breakthrough of the solid-state adsorbent containing alkali metal permanganate was about 48 hours after the start of adsorption. From these results, it was found that ammonia and nitrogen monoxide contained in nitrous oxide can be effectively removed at the same time by combining Molecular Sieve 3A with a solid adsorbent containing soda lime and alkali metal permanganate as an adsorbent.

[Example 6: Removal of carbon dioxide, nitrogen dioxide]

3, purification of crude nitric oxide containing carbon dioxide and nitrogen dioxide as impurities was carried out under a pressurizing condition. The adsorption temperature was set at 60 占 폚. The content of carbon dioxide in the crude nitric oxide was 530 ppm by volume and the content of nitrogen dioxide was 30 ppm by volume and was prepared by mixing carbon dioxide, nitrogen dioxide, and nitrous oxide with a mass flow meter.

The liquefied gas supplied from the bomb charged with nitrogen oxynitride was vaporized by passing through a piping heated to 80 DEG C by an oil bath not shown in the figure and the temperature was raised to 60 DEG C by a heater not shown in the figure, Of nitrogen oxide gas. Then, a nitrogen oxynitride gas was introduced into two adsorption columns as in Example 5. The conditions of introduction of nitrogen oxynitride into the adsorption column were set at a linear velocity of 0.25 m / min and a space velocity of 75.

Nitrous oxide discharged from the adsorption tower loaded with Molecular Sieve 3A was analyzed by FT-IR and the content of carbon dioxide, nitrogen dioxide and water in the nitrous oxide was measured. As a result, it was found that the content of carbon dioxide, which was less than 1 ppm by volume, became more than 1 ppm by adsorption of soda lime as an adsorbent after about 78 hours from the start of adsorption, and the content of water which was less than 1 ppm by volume was the adsorbent Molecular Sieve 3A Was found to be more than 1 ppm by volume after about 87 hours from the start of adsorption. Nitrogen dioxide did not break through.

From this result, it was found that the combination of the solid adsorbent containing soda lime and alkali metal permanganate as the adsorbent with the molecular sieve 3A effectively removes carbon dioxide and nitrogen dioxide contained in the nitrous oxide simultaneously, and effectively removes water released from the soda lime I could see what I could do.

[Example 7: Removal of carbon dioxide, nitrogen dioxide, oxygen, nitrogen]

Purification of crude nitric oxide containing carbon dioxide, nitrogen dioxide, oxygen, and nitrogen as impurities was carried out using a refining facility similar to that of Fig. In this purification, first, carbon dioxide and nitrogen dioxide were removed by an adsorption process using an adsorption tower, and then oxygen and nitrogen were removed by a distillation process using a distillation column.

Also, the content of carbon dioxide in the nitric oxide nitrogen was 530 ppm by volume, the content of nitrogen dioxide was 30 ppm by volume, the content of oxygen was 280 ppm by ppm, and the content of nitrogen was 520 ppm by volume, and the content of carbon dioxide, nitrogen dioxide, oxygen , Nitrogen, and nitric oxide nitrogen.

The liquefied gas supplied from the bomb charged with nitrogen oxynitride was vaporized by passing through a piping heated to 80 DEG C by an oil bath not shown in the figure and the temperature was raised to 60 DEG C by a heater not shown in the figure, Of nitrogen oxide gas. Then, nitrogen oxynitride gas was introduced into two adsorption columns as in Example 6, and adsorption was carried out at a temperature of 60 ° C under a pressurizing condition. The conditions of introduction of nitrogen oxynitride into the adsorption column were set at a linear velocity of 0.25 m / min and a space velocity of 75.

The nitrous oxide passed through two adsorption towers was supplied to the distillation column at a flow rate of 195 g / h. The pressure was 3.6 MPa, the temperature was 7 ° C, the discharge amount of the low boiling point component from the low boiling point component discharge pipe was 5 g / h, Distillation was performed by setting the discharge amount of nitrous oxide to 190 g / h. The distillation column had an inner diameter of 20 mm and a height of 5.5 m, and approximately 1.4 L of Dixson packing (diameter 6 mm) as a distillation packing was filled.

Nitrous oxide discharged from the adsorption tower loaded with Molecular Sieve 3A was analyzed by FT-IR and the content of carbon dioxide, nitrogen dioxide and water in the nitrous oxide was measured. As a result, it was not detected with respect to carbon dioxide, nitrogen dioxide, and water, and the oxygen content was 280 ppm by volume and the nitrogen content was 520 ppm by volume. In addition, as a result of analyzing the nitrous oxide discharged from the high purity nitrous oxide exhaust pipe, the content of oxygen was 0.3 ppm by volume and the content of nitrogen was 0.5 ppm by volume.

10: Adsorption tower
20: Adsorption tower
30: Distillation tower

Claims (8)

A method for purifying nitrous oxide containing at least one of carbon dioxide, nitrogen dioxide, nitrogen monoxide and ammonia as an impurity, comprising the steps of: preparing a solid adsorbent containing calcium hydroxide, a solid adsorbent containing Molecular Sieve 3A and a solid adsorbent containing an alkali metal permanganate Introducing the adsorbent into the adsorption column to bring the nitrous oxide into contact with the solid adsorbent containing the calcium hydroxide, the solid adsorbent containing the Molecular Sieve 3A and the solid adsorbent containing the alkali metal permanganate to remove the impurities from the nitrous oxide Wherein the step of adsorbing nitrogen dioxide comprises the step of adsorbing nitrogen dioxide. delete The method according to claim 1,
Contacting the nitrous oxide with the solid adsorbent containing calcium hydroxide and then contacting the solid adsorbent containing the molecular sieve 3A with the solid adsorbent containing calcium hydroxide. delete The method according to claim 1,
Contacting the nitrous oxide with the solid adsorbent containing calcium permanganate and further contacting the solid adsorbent containing the alkali metal permanganate and then further contacting the solid adsorbent containing the molecular sieve 3A with Nitrogen refining method. The method according to claim 1 or 3,
Wherein the adsorption step is carried out under a pressurized condition. The method according to claim 1 or 3,
Further comprising a distillation step of distilling the nitrous oxide. 8. The method of claim 7,
Wherein the nitrous oxide further contains at least one of nitrogen and oxygen as an impurity, and the distillation step comprises removing at least one of nitrogen and oxygen.

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