KR20140041339A - Method for purifying nitric oxide - Google Patents

Abstract

The present invention is to provide a nitric oxide purification method and a purification system which is suitable for obtaining a nitric oxide gas of high purity by suppressing a byproduct formation. A nitric oxide purification method of the present invention in order to achieve the above objective comprises an adsorption process for through-flowing mixing gas containing at least nitric oxide and moisture to inorganic adsorbents and adsorbing moisture to the corresponding adsorbent and uses a pretreatment-completed adsorbent pre-treated in advance for forming inorganic acid salts for the inorganic adsorbents. The present invention provides a system for performing such a nitric oxide purification method.

Description

Purification method of nitrogen monoxide {METHOD FOR PURIFYING NITRIC OXIDE}

The present invention relates to a method and system for purifying nitrogen monoxide.

Nitrogen monoxide can be used, for example, as a material gas for forming an oxynitride film or SiON film on a silicon surface in a semiconductor process. Nitrogen monoxide can be produced by various methods, such as ammonia oxidation, a method of reacting sodium nitrite with ferrous chloride, or a method of reacting nitric acid with sulfurous acid gas, but generally, in a crude nitrogen monoxide gas, Water, but acidic gases such as nitrogen dioxide and sulfur dioxide are included as impurities or by-products. In particular, in the method of producing nitric oxide by reducing nitric acid to sulfur dioxide, sulfur dioxide is contained as an impurity in the crude nitrogen monoxide. In order to form the above-mentioned oxynitride film in a semiconductor process, it is desired that it is high purity with respect to nitrogen monoxide as a material gas.

As a relatively simple method of purifying or purifying nitrogen monoxide, a method of flowing crude nitrogen monoxide gas (mixed gas) through an inorganic adsorbent such as activated aluminum oxide, zeolite, and silica gel under predetermined conditions is known. According to this method, mainly moisture in a mixed gas is adsorbed by an inorganic type adsorbent, and it removes. Such a method using an inorganic adsorbent is described in, for example, Patent Document 1 and Patent Document 2 below. In patent document 1, in order to refine | purify nitrogen monoxide containing water, nitrogen dioxide, and sulfur dioxide, silica, aluminum oxide, zeolites, and these mixtures which do not contain a metal cation are used as an adsorbent. In patent document 2, in order to adsorb | suck and remove water and nitrogen oxide from a gas stream, nitrogen oxide is removed by zeolite Y containing 8 to 30% of metal cations by dehydrating with silica.

However, in the above-mentioned conventional method for purifying nitrogen monoxide using an inorganic adsorbent, water in the mixed gas is effectively adsorbed and removed, but mixed by an impurity byproduct reaction of nitrogen monoxide (for example, 3NO to N ₂ O + NO ₂ ). It is known that the amount of nitrogen dioxide and nitrogen oxide in the gas may be increased. Therefore, in the prior art, even if a special adsorbent is used, nitrogen monoxide of high purity is not sufficiently obtained.

As another method of purifying nitrogen monoxide, which is relatively simple, a method of bringing a mixed gas into contact with an aqueous alkali solution is known from the past. According to this method, mainly nitrogen dioxide and sulfur dioxide in a mixed gas are absorbed and removed by aqueous alkali solution.

However, in the conventional nitrogen monoxide purification method using an aqueous sodium hydroxide solution as an aqueous alkali solution, however, nitrogen dioxide and sulfur dioxide in the mixed gas are removed, but water remains in the purified gas, and water removal is necessary.

Moreover, in patent document 3, the method of carrying out the deep cooling separation at -164 degreeC using liquid nitrogen as a method of refine | purifying another nitrogen monoxide is disclosed. However, in this technique, the cooling operation by liquid nitrogen is complicated, the apparatus is expensive, and there is also the possibility of explosive liquid nitrogen monoxide, which cannot be said to be suitable for industrialization.

JPH8-319104 A JPS51-141784 A KR 20100007188 A

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and a system for purifying nitrogen monoxide, which is suitable for obtaining a high-purity nitrogen monoxide gas by suppressing the formation of by-products.

According to the first aspect of the present invention, there is provided a method for purifying nitrogen monoxide, comprising an adsorption step of adsorbing a mixed gas containing at least nitrogen monoxide and water into an inorganic adsorbent to adsorb moisture to the adsorbent. A method for purifying nitrogen monoxide is provided, characterized by using a pretreated adsorbent pretreated with a pretreatment for producing an inorganic acid salt. The inorganic acid salt here is represented by nitrate, and sulfate, phosphate, hydrochloride, etc. are illustrated in addition.

When a crude nitrogen monoxide gas (hereinafter referred to as "mixed gas") is passed through an adsorbent to adsorb and remove impurities from the mixed gas, an impurity by-product reaction of nitrogen monoxide is suppressed by performing a predetermined pretreatment on the inorganic adsorbent in advance. The inventors have found that. Specifically, for example, when a relatively polar mine solution is brought into contact with the inorganic adsorbent as a pretreatment, part of the mine causes chemical adsorption with the inorganic adsorbent to produce an inorganic acid salt. It is believed that the catalytically active point due to the impurity byproduct reaction of nitrogen monoxide is in a blocked state. Therefore, according to the method for purifying nitrogen monoxide according to the present invention, it is possible to reduce the amount of by-products produced by the impurity byproduct reaction of nitrogen monoxide in the adsorption step. Therefore, this method is preferred for obtaining higher purity nitrogen monoxide.

Preferably, the pretreatment includes an operation of bringing the aqueous mineral solution into contact with the inorganic adsorbent. In this case, it is preferable that the said photo-acid aqueous solution is nitric acid aqueous solution.

Preferably, the pretreatment includes an operation of bringing an acidic gas into contact with the inorganic adsorbent.

According to one embodiment of the present invention, the mixed gas contains at least one of nitrogen dioxide and sulfur dioxide as impurities, and the mixed gas is brought into contact with an aqueous alkali solution before the mixed gas is supplied to the adsorption step, so that the impurities An alkali washing step for absorbing and removing (nitrogen dioxide or sulfur dioxide) is further included.

According to the method of the present invention, even in the case where the mixed gas contains nitrogen dioxide or sulfur dioxide as impurities, in the alkali washing step, nitrogen dioxide and sulfur dioxide can be absorbed and removed by the aqueous alkali solution. Thus, the process of the present invention is suitable for obtaining high purity nitrogen monoxide.

According to a second aspect of the present invention, there is provided a nitrogen monoxide purification system including an adsorption tube filled with an inorganic adsorbent for adsorbing and removing moisture from a mixed gas containing at least nitrogen monoxide and water, wherein the inorganic adsorbent is an inorganic acid salt. A nitrogen monoxide purification system is provided, characterized in that a pretreatment for production is performed in advance.

Preferably, the inorganic acid salt is nitrate.

According to one embodiment of the second aspect of the present invention, the mixed gas further contains one of nitrogen dioxide and sulfur dioxide as an impurity, and for removing and removing the impurities from the mixed gas on an upstream side of the adsorption tube. An absorbing liquid contact device containing an aqueous alkali solution is provided.

1 is a schematic structural diagram of a purification system that can be used to carry out a method for purifying nitrogen monoxide according to the present invention.

Next, preferred embodiment of this invention is described based on an accompanying drawing. However, embodiment described below is a mere illustration and does not limit the scope of the present invention.

1 is a schematic structural diagram of a purification system X1 that can be used to carry out the nitrogen monoxide (NO) purification method according to the present invention. The refining system X1 includes an absorbent liquid contact device 1 for removing nitrogen dioxide (NO ₂ ) and sulfur dioxide (SO ₂ ) and water (H ₂ ) in order to purify the crude NO gas supplied from the NO cylinder (Y1). O) Adsorption tube (2) for removal, pressure regulating valve (3), on / off valves (4A) to (4E), product NO outlet (5), and purge gas inlet (6) And a gas outlet 7, a vacuum pump 8, and a pipe connecting them.

The NO cylinder Y1 is for supplying crude NO gas as the source gas (mixed gas) to the purification system X1, and crude NO gas is sealed under high pressure conditions. The crude NO gas encapsulated contains NO as a main component and NO ₂ , SO ₂ and H ₂ O as impurities.

The absorbent liquid contact device 1 is for bringing a raw material gas into contact with an aqueous alkali solution which is an absorbent liquid, and includes an absorbent liquid tank 1A, a gas introduction pipe 1a, a gas outlet 1b, an absorbent liquid supply port 1c, and a liquid discharge port. (1d) is included. The absorbing liquid tank 1A has a container shape, and is filled with an aqueous alkali solution having NO ₂ absorbing capacity and SO ₂ absorbing capacity therein. The gas introduction pipe 1a extends downward in the inside of the absorption liquid tank 1A, and the lower end part is open | released in aqueous alkali solution. The absorbent liquid supply port 1c is a passage for supplying a new alkaline aqueous solution into the absorbent liquid tank 1A. The liquid discharge port 1d is a passage for discharging the alkaline aqueous solution in the absorbent liquid tank 1A out of the absorbent liquid tank 1A.

As aqueous alkali solution, aqueous solution, such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, can be employ | adopted, for example. Among these, an aqueous sodium hydroxide solution is preferred from the viewpoint of ease of handling and the like.

The absorbent liquid contact device 1 is preferably configured to discharge the source gas into the aqueous alkali solution in a microbubble form from the viewpoint of efficiently bringing the source gas into contact with the aqueous alkali solution. Since the configuration for discharging the source gas in the form of microbubbles is well known, it is not shown in FIG.

The adsorption pipe 2 is comprised so that a gas can pass through, and has a cylindrical shape in this embodiment. The adsorption tube 2 is filled with an inorganic adsorbent having H ₂ O adsorption capacity, NO ₂ adsorption capacity, and SO ₂ absorption capacity. Examples of such inorganic adsorbents include activated aluminum oxide, zeolite and silica gel. Among these, activated aluminum oxide and zeolite of type A are generally used for dehydration. As described later, these adsorbents are subjected to a predetermined pretreatment prior to the purification of NO. Moreover, the temperature adjusting mechanism (not shown) for adjusting the internal temperature is attached to the suction pipe 2.

The pressure regulating valve 3 reduces the source gas supplied from the NO cylinder Y1 and adjusts it to a predetermined pressure. The open / close valves 4A to 4E are each selectable in an open state and a closed state in which gas is allowed to pass.

As described above, in the NO purification method, a predetermined pretreatment for producing an inorganic acid salt is performed on the inorganic absorbent filled in the adsorption pipe 2 prior to performing purification of NO using the purification system X1. Do it.

The pretreatment is performed by contact between the aqueous solution of mineral acid and the inorganic adsorbent. The contact of the aqueous mineral solution with the inorganic adsorbent can be performed by, for example, impregnating the inorganic mineral adsorbent with the aqueous mineral solution. As the photo acid, for example, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and the like can be used. Among these, since the by-product in NO purification is nitric acid, use of nitric acid is preferable from a viewpoint of the prevention of a foreign material mixing. When the nitric acid aqueous solution as the mineral acid aqueous solution is brought into contact with the inorganic adsorbent, nitrates are produced to obtain a pretreated adsorbent. Here, although the density | concentration of the photo-acid aqueous solution to be used is not specifically limited, Usually, the aqueous photo-acid solution of 0.01-1 prescription is used. Impregnation of the mineral aqueous solution with the inorganic absorbent may be performed for, for example, about 1 to 20 hours outside the purification system (X1). 10 hours or more is required for impregnation when leaving the aqueous solution of mineral acid and the adsorbent at room temperature without stirring, but about 2 hours when stirring at 40 to 50 ° C. The adsorbent is then filtered and dried. As a drying method, although pressure reduction drying or hot air drying has high efficiency, it may be a drying method using stationary drying and a conical dryer. The dried and impregnated adsorbent is stored in the storage container, but is nitrogen-substituted and stored in the air in the storage container so as not to absorb moisture during storage. However, the adsorbent pretreated as mentioned above may be filled into the adsorption pipe 2 immediately after pretreatment, without preserving.

In addition, the pretreatment which concerns on this invention is not limited to the wet method mentioned above, You may perform by dry contact of an acidic gas and an inorganic type adsorption agent. For example, a gas containing an inorganic adsorbent and an acidic gas such as NO ₂ or SO ₂ is injected into a vessel capable of pressurization such as an autoclave, and maintained at 0.1 to 1.5 MPa for several hours at 30 to 60 ° C. You may perform preprocessing by doing this. Here, an inert gas such as nitrogen, argon (Ar), helium (He), or a gas such as NO which is not a problem even when mixed into the product gas may be used as a dilution gas for acidic gas. The pretreated adsorbent thus obtained may be filled in the adsorption tube 2 immediately after the pretreatment is finished, or may be filled in the adsorption tube 2 after being stored in a storage container.

By performing the above-mentioned pretreatment, NO refining is performed using the refining system X1 in a state in which the pretreated adsorbent is filled in the adsorption tube 2. First, on-off valves 4A and 4C are opened and on-off valves 4B, 4D and 4E are closed. Then, the raw material gas (crude NO gas) is continuously supplied from the NO cylinder Y1 to the absorbent liquid contact device 1 via the pressure regulating valve 3, and the absorbent liquid contact device 1 performs an alkali cleaning process. . As described above, the source gas contains NO as a main component and NO ₂ , SO ₂ and H ₂ O as impurities. The NO ₂ concentration, SO ₂ concentration, and H ₂ O concentration of the source gas supplied from the NO cylinder Y1 are, for example, 0.1 to 1000 ppm. The pressure set in the pressure regulating valve 3 is, for example. It is 0.05-20 Mpa, Preferably it is 0.1-2 Mpa.

In the alkali washing step, the source gas is brought into contact with the aqueous alkali solution by releasing the source gas from the lower end of the gas introduction pipe 1a to absorb the non-absorbing gas after absorbing NO ₂ and SO ₂ as impurities into the aqueous alkali solution. It is led out of the absorbent liquid contact device 1 from the outlet 1b. In addition, in the alkali washing step, a new alkaline aqueous solution is replenished at a constant flow rate through the absorbent liquid supply port 1c, and the aqueous alkali solution contained in the absorbent liquid tank 1A is absorbed from the liquid outlet 1d at a constant flow rate. ) Out. The temperature of the aqueous alkali solution in the absorption liquid tank 1A is 10-50 degreeC, for example, Preferably it is 20-40 degreeC.

The raw material gas (non-absorption gas) which completed the alkali washing process in the absorbent liquid contact apparatus 1 then reaches the adsorption pipe 2 through the opening / closing valve 4A, and is provided to an adsorption process. In the adsorption process, and the adsorption tube (2) pre-finished contact a non-absorbing gas in the adsorbent and, the non NO _2, in the impurities H ₂ O, NO _2, SO ₂ (prior alkali washing step of remaining in the absorbing gas SO ₂ in the Since most of is removed, the main impurity in the adsorption process is H ₂ O), and the non-adsorbed gas is led out of the adsorption tube 2 after adsorption or retention in the pretreated adsorbent. The internal temperature of the adsorption tube 2 is -40-50 degreeC, for example, Preferably it is 0-40 degreeC. In this embodiment, since nitrate is produced in the pretreated adsorbent, the catalytically active point of the inorganic adsorbent is considered to be in a blocked state. Therefore, in the adsorption step, the impurity byproduct reaction with respect to NO is suppressed, and the amount of N ₂ O and NO ₂ generated by the impurity byproduct reaction is reduced. The adsorption step is, for example, H ₂ O is sufficiently absorbed, and, running up to the breakthrough point (break-through point) is (破過) is started, it may be terminated prior to the break through point. The adsorption step can be completed by keeping the on-off valve 4C closed and the on-off valve 4D open while continuously supplying source gas from the NO cylinder Y1 to the purification system X1. Until the end of the adsorption step, the gas passed through the adsorption tube 2 can be discharged from the product NO outlet 5 as purified NO gas.

As described above, a crude NO gas (raw material gas) containing NO ₂ , SO ₂ and H ₂ O as impurities can be purified to obtain a high purity NO gas.

In order to repeatedly execute the NO gas purification method according to the present invention in the refining system X1, the adsorption pipe 2 to the adsorbents therein are regenerated or washed after the refining process as described above.

At the time of regeneration or cleaning of the adsorption tube 2 to the internal pretreated adsorbent, the on / off valves 4A, 4C and 4E are closed and the on / off valves 4B and 4D are open. do. Then, inert gas is continuously introduced into the purification system X1 from the purge gas introduction port 6. The inert gas introduced from the purge gas inlet 6 is previously heated up to a predetermined temperature by a heater (not shown), and the gas outlet (eg, through the on / off valve 4B, the suction tube 2 and the on / off valve 4D) 7) out of the line. As the inert gas, for example, there may be employed a N ₂ or argon (Ar), helium (He). The temperature of the inert gas heated by the said heater is 100-300 degreeC, for example, Preferably it is 150-250 degreeC. In this manner, the adsorption tube 2 to the pretreated treated adsorbent can be regenerated or washed by passing an inert gas of a predetermined amount and a predetermined pressure therethrough.

According to the above-NO purification method, the alkaline washing step of the absorbing liquid in the contact device (1) can be removed by absorbing the NO ₂ or SO ₂ in the feed gas in an alkaline aqueous solution. Thus in addition, NO is the by-product impurities of the reaction inhibited by the adsorption process at the suction tube (2), using the pre-treatment complete, the adsorbent, a by-product of production of N ₂ O and NO ₂ is reduced. In this way, when the source gas contains NO ₂ , SO ₂ , H ₂ O as impurities, the NO ₂ , SO ₂ and H ₂ O are effectively removed in the alkaline washing step and the adsorption step, and in each step The amount of by-products produced can be reduced, and high purity NO is obtained.

In the source gas supplied from the NO cylinder Y1, in the case where the NO ₂ and SO ₂ are substantially not contained or the NO ₂ content and the SO ₂ content are small, the alkali washing step may be omitted. In this case, the purification system for performing the NO purification method does not include the absorbent liquid contact device 1.

Below, this invention is demonstrated in detail based on Examples 1-4 and a comparative example.

[Example 1]

In Example 1, the absorption liquid contacting apparatus 1 in the said embodiment (FIG. 1) is abbreviate | omitted, and the adsorption process is performed in the adsorption pipe 2 with respect to the crude NO gas supplied from the NO cylinder Y1. It was. Activated aluminum oxide (trade name: KHD-12, manufactured by Sumitomo Chemical Co., Ltd.) was used as the inorganic adsorbent to be filled in the adsorption tube 2. As adsorbent pretreatment, 18.6 g of active aluminum oxide was mixed and stirred with 0.3 N aqueous nitric acid solution at 40 ° C for 2 hours, and then vacuum dried at 60 ° C for 6 hours. The preprocessed adsorbent thus obtained was filled into the adsorption tube 2 (a stainless steel cylindrical adsorption tube having an internal diameter of 7.5 mm and a length of 500 mm). Thereafter, the vacuum pump 8 is operated by raising the suction pipe 2 to 150 ° C, closing the on-off valves 4A to 4D and opening / closing the valve 4E. Vacuum suction was performed for about 2 hours so that the pressure in the pipe 2 became 270 kPa (absolute pressure). Next, crude NO gas (H ₂ O content = 100 ppm, NO ₂ content = 500 ppm, N ₂ O content = 50 ppm) as source gas was flowed into the adsorption tube 2 at 25 ° C. under a pressure of 0.15 MPaG. . The flow rate of source gas into the adsorption tube 2 was 60 ml / min. In this way, the adsorption step was performed. After 1 hour from the start of the flow, the non-adsorbed gas from the adsorption tube 2 was analyzed by dew point meter and FT-IR. H ₂ O content = 1 ppm, NO ₂ content = 30 ppm, and N ₂ O content = 65 ppm, and the increase in N ₂ O content before and after the flow was 15 ppm.

[Example 2]

In Example 2, in place of the active aluminum oxide of Example 1, a molecular sieve 4A (trade name: Zeoram A-4, manufactured by Toso Corporation) was used as the inorganic adsorbent. NO purification (pretreatment and adsorption step) was performed in the same manner as in Example 1 except for the change of the inorganic adsorbent. When 1 hour elapsed after the start of source gas flow into the adsorption tube 2, the non-adsorption gas derived from the adsorption tube 2 was analyzed. As a result, H ₂ O content = 1 ppm, NO ₂ content = 25 ppm, and N ₂ O content = 60 ppm and the increase in N ₂ O content before and after the flow was 10 ppm.

[Example 3]

In Example 3, 150 ml of activated aluminum oxide (trade name: KHD-12, manufactured by Sumitomo Chemical Co., Ltd.) was injected into a stainless steel autoclave having an internal pressure of 3 MPa with a content of 300 ml as an adsorbent pretreatment, and NO / NO ₂ The mixed gas of = 1/1 was added until it became 1.5 MpaG. After holding at 40 ° C for 4 hours, the gas was purged, and again, a gas of NO / NO ₂ = 1/1 was added until it became 1.5 MPaG and kept at 30 ° C for 5 hours. The adsorbent pretreated in this way was filled in the adsorption tube 2 similar to Example 1, and refine | purification was performed in the source gas supply aspect similar to Example 1. When 1 hour after the start of the flow, the non-adsorbed gas derived from the adsorption tube 2 was analyzed. As a result, H ₂ O content = 1 ppm, NO ₂ content = 30 ppm, and N ₂ O content = 63 ppm, The increase in N ₂ O content was 13 ppm.

Example 4

In Example 4, the alkali cleaning process and the adsorption process were performed using both the absorbing liquid contacting apparatus 1 and the adsorption tube 2 in the said embodiment (FIG. 1). In this example, 500 ml of an aqueous 1% by weight aqueous sodium hydroxide solution was filled into an aqueous solution contactor 1 having a volume of 1000 ml. The adsorption tube 2 was filled with the activated aluminum oxide pretreated similarly to Example 1, and the temperature rising and the vacuum exhaust were performed. Next, the crude NO gas (H ₂ O content = 100 ppm, NO ₂ content = 500 ppm, SO ₂ content = 500 ppm, N ₂ O content = 50 ppm) as source gas was contacted with the absorbent liquid at 25 ° C. under a pressure of 0.15 MPaG. It flowed through the apparatus 1 and the adsorption pipe 2. When 1 hour after the start of source gas flow through the absorbent liquid contact device 1 and the adsorption tube 2, the non-adsorption gas derived from the adsorption tube 2 was analyzed. As a result, H ₂ O content = 1 ppm and NO ₂ content = 10 ppm, SO ₂ content = less than 1 ppm, N ₂ O content = 63 ppm, and the increase in N ₂ O content before and after the flow was 13 ppm.

[Comparative Example]

In the comparative example, NO purification was performed similarly to Example 1 using the adsorption pipe 2 and the inorganic type adsorption agent (absorbing liquid contact device 1 is omitted), without performing pretreatment. The adsorption tube 2 is filled with 18.6 g of activated aluminum oxide (trade name: KHD-12, manufactured by Sumitomo Chemical Co., Ltd.), and the adsorption tube 2 is heated to 150 ° C. ), The on-off valve 4E was opened, the vacuum pump 8 was operated, and vacuum suction was performed for about 2 hours so that the pressure in the suction tube 2 was 270 kPa (absolute pressure). Next, crude NO gas (H ₂ O content = 100ppm, NO ₂ content = 500ppm, N ₂ O content = 50ppm) as source gas was flowed into the adsorption tube 2 at 25 ° C under a pressure of 1.5 MPaG. . The flow rate of source gas into the adsorption tube 2 was 60 ml / min. In this way, the adsorption step was performed. That is, in the comparative example, NO purification was performed similarly to Example 1 except not having performed pretreatment. When 1 hour elapsed after the start of source gas flow into the adsorption tube 2, the non-adsorption gas derived from the adsorption tube 2 was analyzed. As a result, H ₂ O content = 1 ppm, NO ₂ content = 30 ppm, and N ₂ O content = 250 ppm and the increase in N ₂ O content before and after the flow was 200 ppm.

[evaluation]

Examples 1 to 4 of the N ₂ O As you can understand comparing the content increase and the comparative example N ₂ O content of the increase, the adsorption process in the embodiment, compared to Comparative Example N ₂ significantly decreased O content increment there was. This is considered to be attributable to the fact that the impurity by-product reaction of NO is suppressed and the amount of N ₂ O produced is reduced by performing a predetermined pretreatment on the inorganic adsorbent. In addition, the amount of NO ₂ generated is also reduced by suppressing the impurity by-product reaction. Therefore, it is possible to expect the reduction effect compared to the case about the NO ₂ content increase, not subjected to the pretreatment. As described above, in the examples, the amount of generation of by-products (N ₂ O or NO ₂ ) was reduced by passing through the adsorption step using the pre-treated adsorbent, and as a result, NO was able to be made higher in purity.

X1: Refining System Y1: NO Cylinder
1: absorption contact device 2: adsorption tube
3: pressure regulating valve 4A to 4E: on / off valve
5: product NO outlet 6: purge gas inlet
7: gas outlet 8: vacuum pump

Claims (8)

A process for purifying nitrogen monoxide, comprising adsorbing a mixture gas containing at least nitrogen monoxide and water through an inorganic adsorbent to adsorb moisture to the adsorbent, wherein the pretreatment for producing an inorganic acid salt is performed as the inorganic adsorbent. A method for purifying nitrogen monoxide, characterized by using a pretreated adsorbent previously performed. The method for purifying nitrogen monoxide according to claim 1, wherein the pretreatment includes an operation of bringing the aqueous mineral solution into contact with the inorganic adsorbent. The method of claim 2, wherein the aqueous solution of mineral acid is an aqueous solution of nitric acid. The method for purifying nitrogen monoxide according to claim 1, wherein the pretreatment includes an operation of bringing an acidic gas into contact with the inorganic adsorbent. The mixed gas according to any one of claims 1 to 4, wherein the mixed gas further contains one of nitrogen dioxide and sulfur dioxide as an impurity.
A method for purifying nitrogen monoxide further comprising an alkali washing step of contacting the mixed gas with an aqueous alkali solution to absorb and remove the impurities before performing the adsorption step of the mixed gas. A nitrogen monoxide purification system comprising an adsorption tube filled with an inorganic adsorbent for adsorbing and removing water from a mixed gas containing at least nitrogen monoxide and water, wherein the inorganic adsorbent is pretreated for producing an inorganic acid salt. Nitrogen monoxide purification system, characterized in that. The system of claim 6, wherein the inorganic acid salt is nitrate. The mixed gas according to claim 6 or 7, further comprising one of nitrogen dioxide and sulfur dioxide as an impurity,
The nitrogen monoxide purification system provided with the absorbing-liquid contact apparatus which accommodated the aqueous alkali solution for contacting and removing the said impurity from the said mixed gas on the upstream side of the said adsorption tube.

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