JP2012211060A - Method for producing argon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing argon, with which high-purity argon is obtained by suppressing occurrence of methane.SOLUTION: In the method for producing argon, raw material air is separated into gaseous nitrogen and oxygen by distillation, an intermediate component in which argon is concentrated is extracted and rectified, and crude gaseous argon including small amounts of oxygen and nitrogen is obtained, and subsequently the high-purity argon is produced by purifying the obtained crude argon. The method includes a deoxidation step to add hydrogen to the crude gaseous argon and to remove oxygen in the gaseous argon with a catalytic reaction, and in the deoxidation step, a change of carbon monoxide in the crude gaseous argon into methane is suppressed by using a catalyst with low activity.

Description

  The present invention relates to a method for producing high-purity argon by purifying crude argon obtained by a cryogenic air separation method.

  In the method of producing argon by cryogenic air separation, first, the raw material air is separated into nitrogen gas and oxygen by distillation, an intermediate component enriched in argon is extracted and rectified, and a small amount of oxygen and nitrogen is removed. A crude argon gas containing is obtained. Next, hydrogen is added to the obtained crude argon gas, and oxygen in the argon gas is removed by a catalytic reaction (hereinafter referred to as a deoxygenation step). Next, hydrogen in the argon gas is rectified and removed in a high purity argon tower. Thereby, highly purified argon can be obtained (for example, refer patent documents 1 and 2).

JP 59-145473 A Japanese Patent Publication No. 8-32550

By the way, in the deoxygenation process mentioned above, it aims at reaction of following formula (1).
H ₂ + 1 / 2O ₂ → H ₂ O (1)

However, the crude argon gas contains a few ppm of a small amount of carbon monoxide together with several percent of oxygen, and this carbon monoxide is the heat of reaction during the deoxygenation step as shown in the following formula (2). To methane.
CO + 3H ₂ → CH ₄ + H ₂ O (2)

  For this reason, in the deoxidation process mentioned above, methane will be contained in argon. In this case, in the rectification process in the high-purity argon tower, separation of argon and hydrogen is mainly performed, so that carbon monoxide having a higher boiling point than argon can be removed, but methane having a low boiling point (−164 ° C.) It remains in argon.

  In response to such a problem, Patent Document 2 discloses that methane is generated by adding an excessive amount of hydrogen and controlling the temperature in the deoxidation catalyst layer to 230 ° C. or lower or 480 ° C. or higher. A method for producing suppressed argon is disclosed.

  However, when it is desired to use such a method, when the oxygen concentration in the crude argon exceeds several percent, the temperature in the deoxygenation catalyst layer increases, and it becomes difficult to control the temperature. A problem will occur.

  This invention is proposed in view of such a conventional situation, and it aims at providing the manufacturing method of argon which suppressed generation | occurrence | production of methane and made it possible to obtain high purity argon. .

  In order to achieve the above object, the method for producing argon according to the present invention separates raw material air into nitrogen gas and oxygen by distillation, extracts an intermediate component enriched in argon, and rectifies it to produce a small amount of oxygen. After obtaining the crude argon gas containing nitrogen, the obtained crude argon is purified to produce high-purity argon, in which hydrogen is added to the crude argon gas and oxygen in the argon gas is catalyzed. In this deoxygenation step, a change in carbon monoxide in the crude argon gas to methane is suppressed using a catalyst having low activity.

  As described above, according to the present invention, generation of methane can be suppressed and high-purity argon can be obtained.

FIG. 1 is a flow sheet showing an example of a production apparatus for carrying out the production of argon according to the present invention.

Hereinafter, a method for producing argon to which the present invention is applied will be described in detail with reference to the drawings.
FIG. 1 is a flow sheet showing an example of a production apparatus 1 for carrying out the production of argon according to the present invention.

  In this production apparatus 1, as shown in FIG. 1, after the raw air introduced into the main rectifying tower lower tower 2 passes through the main rectifying tower upper tower 3, most of nitrogen and oxygen are removed, Introduced into the crude argon column 4. And it is further rectified in the crude argon tower 4, and the crude argon gas containing a small amount of oxygen and nitrogen is produced | generated.

  In the production apparatus 1, the crude argon gas introduced into the argon purification apparatus 5 passes through the heat exchanger 6 and the crude argon compressor 7 and is introduced into the deoxygenation tower 8. The deoxygenation tower 8 is filled with a catalyst, hydrogen is added to the crude argon gas, and oxygen content is removed by a catalytic reaction (hereinafter referred to as deoxygenation step).

 The modified argon gas modified by the above reaction passes through the heat exchanger 9 and is sent to the dehumidifier 10 and is returned to the inlet of the deoxygenation tower 8 by the circulation blower 11. Therefore, the crude oxygen gas diluted with the modified argon gas is actually introduced into the deoxygenation tower 8.

  Thereby, since the oxygen concentration in the gas introduced into the deoxygenation tower 8 decreases, the reaction temperature by the catalyst can be lowered. That is, when the crude argon gas is introduced as it is, the reaction temperature of about 300 to 400 ° C. can be reduced to 230 ° C. or less.

  The denatured argon gas is brought into contact with the adsorbent in the dehumidifier 10 to remove water as a reaction product. Then, it passes through the heat exchanger 6 again and is introduced into the purified argon column 12. In the purified argon column 12, low boiling impurities such as nitrogen and hydrogen are purified and separated by distillation, and high purity liquefied argon is taken out.

  By the way, in the argon production method to which the present invention is applied, in the deoxygenation step, a catalyst having low activity is used to suppress the change of carbon monoxide in the crude argon gas to methane.

  Specifically, in the present invention, after adding an amount of hydrogen capable of sufficiently reducing oxygen contained in the crude argon gas to the crude argon gas obtained by the cryogenic air separation method, the catalyst is brought into contact with the catalyst. Then, oxygen is converted into water by the reaction of the above formula (1). At this time, by using a catalyst having low activity, carbon monoxide contained in the crude argon gas is prevented from reacting with hydrogen and generating methane.

As such a low activity catalyst, a palladium catalyst made of aluminum oxide (active alumina) supporting palladium can be used. Moreover, as a palladium catalyst, it is preferable to use a thing whose specific surface area by BET method is 60 m < ² > / g or less. Moreover, as a palladium catalyst, it is preferable to use a metal specific surface area of 20 m ² / g or less by a carbon monoxide adsorption method (CO adsorption method). Furthermore, the reaction temperature of the catalyst when such a low activity catalyst is used is preferably 350 ° C. or lower.

  Thereby, it is possible to suppress the generation of methane by reacting carbon monoxide contained in the crude argon gas with hydrogen, and to obtain high-purity argon. Further, according to the present invention, it is possible to avoid the problem that the temperature in the deoxygenation catalyst layer as in Patent Document 2 described above increases and temperature control becomes difficult.

In addition, this invention is not necessarily limited to the thing of the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.
For example, in the manufacturing apparatus 1 shown in FIG. 1, a valve can be arranged instead of the circulation blower 11. In this case, a part of the modified argon gas exiting the heat exchanger 9 after the deoxygenation tower 8 is returned to the inlet of the crude argon compressor 7 through this valve.

  When the circulation blower 11 is used, there is an advantage that the return amount of the modified argon gas can be increased. On the other hand, when a valve is used instead of the circulation blower 11, the structure is simplified. There is.

  Hereinafter, the effects of the present invention will be made clearer by examples. In addition, this invention is not limited to a following example, In the range which does not change the summary, it can change suitably and can implement.

Example 1
In Example 1, as shown in Table 1, an active alumina catalyst carrying palladium as a catalyst, the specific surface area measured by the BET method was 14 m ² / g, and the metal surface area measured by the CO adsorption method was 9 using what the .1m ² / g, the filling height was packed so that 200mm of this catalyst deoxygenation column having an inner diameter of 23 mm.

  Then, hydrogen gas is added to an argon gas containing 1.5% oxygen and 1 ppm carbon monoxide so as to have a concentration of 6%, and this argon gas is added at a flow rate of 5 NL / min in the deoxygenation tower. Contacted with catalyst.

  As a result, the temperature of the catalyst rose from 25 ° C. to 250 ° C. due to the reaction between oxygen and hydrogen. And oxygen was not detected in the argon gas discharged | emitted from this deoxygenation tower. Carbon monoxide hardly reacted, and the detected methane was 0.01 ppm.

(Example 2)
In Example 2, as shown in Table 1, an active alumina catalyst carrying palladium as a catalyst, the specific surface area measured by the BET method was 25 m ² / g, and the metal surface area measured by the CO adsorption method was 11 m. using what becomes ^{2 /} g, otherwise, the same conditions as those in example 1, was the argon gas is contacted with the catalyst in the deoxygenation column.

  As a result, the temperature of the catalyst increased from 25 ° C to 250 ° C. And oxygen was not detected in the argon gas discharged | emitted from this deoxygenation tower. Carbon monoxide hardly reacted, and the detected methane was 0.03 ppm.

(Example 3)
In Example 3, as shown in Table 1, an active alumina catalyst carrying palladium as a catalyst, the specific surface area measured by the BET method was 54 m ² / g, and the metal surface area measured by the CO adsorption method was 14 m. using what becomes ^{2 /} g, otherwise, the same conditions as those in example 1, was the argon gas is contacted with the catalyst in the deoxygenation column.

  As a result, the temperature of the catalyst increased from 25 ° C to 250 ° C. And oxygen was not detected in the argon gas discharged | emitted from this deoxygenation tower. Carbon monoxide hardly reacted, and the detected methane was 0.03 ppm.

(Comparative Example 1)
In Comparative Example 1, as shown in Table 1, an active alumina catalyst carrying palladium as a catalyst, the specific surface area measured by the BET method was 240 m ² / g, and the metal surface area measured by the CO adsorption method was 100 m. using what becomes ^{2 /} g, otherwise, the same conditions as those in example 1, was the argon gas is contacted with the catalyst in the deoxygenation column.

  As a result, the temperature of the catalyst rose from 25 ° C to 300 ° C. Moreover, the detected methane was 0.5 ppm.

Example 4
In Example 4, as shown in Table 1, using the same catalyst as in Example 1, hydrogen gas was added to an argon gas containing 2% oxygen and 1 ppm of carbon monoxide so that the concentration would be 8%. The argon gas was brought into contact with the catalyst in the deoxygenation tower at a flow rate of 5 NL / min.

  As a result, the temperature of the catalyst increased from 25 ° C to 320 ° C. And oxygen was not detected in the argon gas discharged | emitted from this deoxygenation tower. Carbon monoxide hardly reacted, and the detected methane was 0.05 ppm.

(Example 5)
In Example 5, as shown in Table 1, the same catalyst as in Example 3 was used, and the argon gas was brought into contact with the catalyst in the deoxygenation tower under the same conditions as in Example 4 except that.

  As a result, the temperature of the catalyst increased from 25 ° C to 320 ° C. And oxygen was not detected in the argon gas discharged | emitted from this deoxygenation tower. Further, carbon monoxide hardly reacted, and the detected methane was 0.15 ppm.

(Comparative Example 2)
In Comparative Example 2, as shown in Table 1, the same catalyst as in Comparative Example 1 was used, and the argon gas was brought into contact with the catalyst in the deoxygenation tower under the same conditions as in Example 4 except that.

  As a result, the temperature of the catalyst rose from 25 ° C to 370 ° C. Moreover, the detected methane was 0.7 ppm.

(Comparative Example 3)
In Comparative Example 3, as shown in Table 1, the same catalyst as in Example 1 was used, and the concentration was 10.0% in argon gas containing 2.5% oxygen and 1 ppm carbon monoxide. Hydrogen gas was added and the argon gas was brought into contact with the catalyst in the deoxygenation tower at a flow rate of 5 NL / min.

  As a result, the temperature of the catalyst rose from 25 ° C to 390 ° C. Moreover, the detected methane was 0.4 ppm.

  DESCRIPTION OF SYMBOLS 1 ... Manufacturing apparatus 2 ... Main rectification tower lower tower 3 ... Main rectification tower upper tower 4 ... Crude argon tower 5 ... Argon purification apparatus 6 ... Heat exchanger 7 ... Crude argon compressor 8 ... Deoxygenation tower 9 ... Heat exchanger DESCRIPTION OF SYMBOLS 10 ... Dehumidifier 11 ... Circulating blower 12 ... Purified argon tower

Claims (5)

The raw material air is separated into nitrogen gas and oxygen by distillation, and an intermediate component enriched with argon is extracted and rectified to obtain a crude argon gas containing a small amount of oxygen and nitrogen. A method for producing high purity argon by purification,
A deoxygenation step in which hydrogen is added to the crude argon gas and oxygen in the argon gas is removed by a catalytic reaction, and in this deoxygenation step, carbon monoxide in the crude argon gas is used using a catalyst having low activity. A method for producing argon, characterized by suppressing the change of methane to methane. ^{2. The} method for producing argon according to claim 1, wherein the catalyst is made of aluminum oxide carrying palladium and has a specific surface area of 60 m ² / g or less by BET method. The said catalyst consists of aluminum oxide which carry | supported palladium, The metal specific surface area by the carbon monoxide adsorption method is 20 m < ² > / g or less, The manufacturing method of argon of Claim 1 or 2 characterized by the above-mentioned.   The method for producing argon according to any one of claims 1 to 3, wherein a reaction temperature by the catalyst is 350 ° C or lower.   After the deoxygenation step, water in argon gas is removed by contact with an adsorbent, and then hydrogen in argon gas is rectified and removed.

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