WO2006035571A1

WO2006035571A1 - Method for producing high-purity liquid chlorine

Info

Publication number: WO2006035571A1
Application number: PCT/JP2005/016157
Authority: WO
Inventors: Minako Horiba; Shozo Yago
Original assignee: Showa Denko K.K.
Priority date: 2004-09-29
Filing date: 2005-08-29
Publication date: 2006-04-06
Also published as: TWI391326B; KR20070028586A; TW200621636A; KR100849656B1; JPWO2006035571A1; JP5219372B2

Abstract

Disclosed is a method for producing high-purity liquid chlorine wherein a raw material chlorine which contains chlorine oxide as impurities is irradiated with light so that the chlorine oxide is decomposed into chlorine and oxygen, and then purification is performed by distillation. Consequently, chlorine oxide impurities can be efficiently removed from chlorine.

Description

Manufacturing method of high purity liquefied chlorine Technical Field

The present invention relates to a method for producing high-purity liquefied chlorine. In particular, the present invention

The present invention relates to a method capable of producing high-purity liquefied chlorine having a purity of 99.999% or more by refining raw material chlorine containing chlorine oxide impurities. Background art

Chlorine oxides such as dichlorine monoxide, chlorine dioxide, dichlorine hexaoxide (chlorine trioxide) are very easy to decompose, and decompose into chlorine and oxygen by the heat and light as shown below.

C 1 ₂ O → C 1 ₂ + 1/2 O 2 (1) C 1 O 2 → 1/2 C 1 2 + ○ 2 (2) C 1 ₂ O ₆ → C 1 ₂ + 3 O ₂ (3) The ratio of the concentration of chlorine oxide, especially chlorine dioxide, in the liquefied chlorine in the gas phase to the liquid phase is about 0.7 compared to the liquid phase 1 and there is no significant difference in concentration. The ratio of the concentration of oxygen, which is a decomposition product of chlorine oxide, in the gas phase and the liquid phase in the liquefied chlorine is overwhelmingly larger than the liquid phase 1 with the gas phase being more than 100 Will exist. At the time of filling, the total amount of impurities is 10 ppm or less, and even if the purity of chlorine is 99.999% or more, chlorine and oxygen are produced when this small amount of chlorine dioxide is gradually decomposed in the container. However, most of the oxygen produced by the decomposition of chlorine dioxide is concentrated on the gas phase side, and the purity decreases as the oxygen concentration in the gas phase becomes more than 100 times that at the time of filling. And semiconductors, 'LCD It will be unsuitable for high purity applications. Therefore, in order to ensure a purity of 99.999% or higher, it is necessary to reduce the concentration of chlorine oxide, especially chlorine dioxide, to at least 0.01 ppm or less.

Chlorine oxides are known to be mixed into chlorine when chlorine is produced by electrolysis of salt. Various processes for producing chlorine and sodium hydroxide by electrolysis of sodium chloride are known. In such a process, a certain concentration of saline was supplied to the anode chamber of the electrolytic cell, and the concentration decreased due to electrolysis. The saline solution is discharged out of the tank as return salt water, and the concentration is adjusted again and supplied to the electrolytic cell. At this time, sodium chlorate is produced as a by-product of electrolysis, so the concentration of sodium chlorate gradually increases when it is circulated as it is. The chlorate is decomposed into chlorine or chlorine dioxide in the diffusion tank with the anode surface acidified, which causes chlorine oxide, especially chlorine dioxide, to be mixed into the chlorine gas.

Conventionally, as a method of suppressing chlorate formation in an electrolytic cell, for example, a method of reducing with hydrochloric acid or a method of decomposing with sulfuric acid is used. However, there is a limit to lowering the pH of salt water, and it is difficult to completely suppress the formation of chlorate, and it is inevitable that chlorine oxide is mixed in chlorine.

On the other hand, methods for removing chlorine oxides in chlorine, particularly chlorine dioxide, include distillation, adsorption removal, etc. as commonly used methods. Also, chlorine and chlorine are easily utilized by utilizing the property that chlorine dioxide is easily decomposed. A method of decomposing into oxygen is known. If the distillation method is used, the boiling point of chlorine is 13.5 ° C, and the boiling point of chlorine dioxide is 11 ° C and there is a difference in boiling point, but the vapor-liquid equilibrium is close to 1 at room temperature. Removal by distillation was difficult. In addition, in the adsorption method, there are few adsorbents that are resistant to chlorine. Since it is small, a large device is required, and further, it is difficult to regenerate due to deterioration due to chlorine, and the frequency of replacement of the adsorbent is increased, resulting in higher costs.

As decomposition and removal methods, thermal decomposition, catalytic decomposition, and photolysis are known. In pyrolysis, chlorine dioxide is known to decompose at a gas temperature of 100 ° C or higher. For example, a shell-and-tube reaction vessel is used, the shell side is heated with steam, and the tube There is a method of flowing chlorine dioxide to the side. However, the method of simply raising the temperature to 100 ° C. or more increases the energy because the decomposition efficiency is low and the entire gas needs to be raised to a uniform temperature. In addition, equipment materials that are resistant to high-temperature chlorine are required, resulting in high costs. In Japanese Patent Laid-Open No. 3-041093, when pyrolysis of chlorine dioxide, radicals are once generated by locally heating to a temperature higher than the decomposition temperature of chlorine dioxide, and chain reaction is performed. Describes a method of finally decomposing into chlorine and oxygen. However, with this method, if the chlorine dioxide concentration with respect to chlorine is less than 0.5%, chlorine dioxide cannot be efficiently decomposed. For example, chlorine dioxide impurities of the order of P pm cannot be efficiently removed. Absent. Chlorine dioxide decomposes gradually even at temperatures below 100 ° C, but the decomposition takes a long time and is not practical. As the catalytic decomposition, for example, Japanese Patent Application Laid-Open No. SHO 50-1390 777 describes a method in which a chlorine oxide containing chlorine dioxide in a gas is brought into contact with activated carbon and reductively decomposed with activated carbon. Yes. However, with regard to the removal of chlorine dioxide from chlorine gas, chlorine is adsorbed on the activated carbon, so the action of activated carbon as a reducing agent cannot be obtained, and it is difficult to remove chlorine dioxide. Japanese Patent Application Laid-Open No. Sho 5 3-990 69 discloses a method in which chlorine dioxide is reacted with iron to remove it as iron oxide and iron chloride. Since iron reacts with chlorine, it is difficult to selectively remove chlorine dioxide. As photodecomposition, JP-A-3-38 2 18 describes a method of decomposing chlorine dioxide by irradiating chlorine dioxide with ultraviolet rays of 1 to 2900 nm. However, since chlorine shows almost the same light absorption as chlorine dioxide, most of the light energy is absorbed by chlorine even if it is irradiated with ultraviolet rays alone. Therefore, more than one energy absorbed by chlorine. Energy is required, so it is not possible to decompose chlorine dioxide efficiently. Disclosure of the invention

An object of the present invention is to provide a method capable of efficiently removing chlorine oxide impurities from chlorine and producing, for example, high purity liquefied chlorine having a purity of 99.999% or more.

The present inventors have found a method capable of efficiently performing photolysis in a method of removing chlorine oxide impurities in chlorine, particularly chlorine dioxide impurities, by photolysis. That is, the present invention provides a method for producing high-purity liquefied chlorine, which comprises irradiating raw material chlorine containing chlorine oxide as an impurity, decomposing the chlorine oxide into chlorine and oxygen, and then performing purification by distillation. provide.

Therefore, this invention consists of the manufacturing method of the high purity liquefied chlorine of following (1)-(10), for example.

(1) In a method for producing high purity liquefied chlorine by refining raw material chlorine containing chlorine oxide as an impurity, the raw material chlorine is irradiated with light and the chlorine oxide impurity is decomposed into chlorine and oxygen by photolysis. A method for producing high-purity liquefied chlorine, comprising: a photolysis step; and a distillation step for removing photolysis products and other impurities by distillation. (2) The method for producing high-purity liquefied chlorine as described in (1) above, wherein the concentration of chlorine oxide impurities is 0.1 to 50 ppm.

(3) The method for producing high-purity liquefied chlorine according to (1) or (2) above, wherein the chlorine oxide impurity is chlorine dioxide.

(4) The method for producing high-purity liquefied chlorine according to any one of (1) to (3) above, wherein the light source for the photolysis step is a light source containing a wavelength in the range of 300 to 500 nm. .

(5) The high-purity liquefaction according to any one of (1) to (4) above, wherein the raw material chlorine is vaporized by a vaporizer before the photolysis step, and the photolysis reaction is performed in the gas phase in the photolysis step. Chlorine production method.

(6) The method for producing high-purity liquefied chlorine according to any one of (1) to (5) above, wherein the photolysis reaction in the photolysis step is a flow-type photolysis reaction.

(7) The method for producing high-purity liquefied chlorine according to any one of the above (1) to (6), wherein the temperature of the photolysis reaction in the photolysis step is 20 to 60 ° C.

(8) The method for producing high-purity liquefied chlorine according to any one of the above (1) to (7), wherein the pressure of the photolysis reaction in the photolysis step is 0.01 to 1.5 MPa.

(9) The method for producing high-purity liquefied chlorine according to the above (1), wherein the distillation step includes a low-boiling distillation step of removing low-boiling impurities including oxygen generated in the photolysis step.

(10) The method for producing high-purity liquefied chlorine according to any one of the above (1) to (9), wherein the purity of the high-purity liquefied chlorine is 99.99 9% or more.

According to the present invention, chlorine oxide in chlorine can be easily and economically and efficiently removed to obtain high-purity liquefied chlorine, particularly high-purity liquefied chlorine having a purity of 99.999% or more. it can. Brief Description of Drawings

FIG. 1 is a schematic diagram showing the steps of the method of the present invention.

FIG. 2 is a schematic diagram of the photolysis apparatus used in the examples.

FIG. 3 is a schematic diagram of the photolysis apparatus used in the examples. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described in detail.

The method for producing high-purity liquefied chlorine of the present invention is to photoly decompose chlorine oxide impurities by irradiating the raw material chlorine with light when producing high-purity liquefied chlorine using liquefied chlorine containing chlorine oxide impurities as a raw material. It includes a process. That is, the production method of the present invention includes a photolysis step of photolyzing chlorine oxide in raw material chlorine containing chlorine oxide impurities, and distillation of oxygen and other impurities generated by decomposition of chlorine oxide. And a distillation step to be further removed.

Among the chlorine oxide impurities, the main substance is chlorine dioxide. As described in Japanese Patent Publication No. 3 — 3 8 2 1 8, chlorine dioxide has the property of decomposing by light and is known to be chlorine and oxygen. The mechanism of chlorine dioxide photodecomposition is not clear, but is presumed as follows.

In the light absorption of chlorine dioxide, it is known that the maximum absorption wavelength is in the vicinity of 37 nm and the absorption band is in the range of 25-50 nm. A reaction that is excited by absorbing light of these wavelengths to generate radicals, for example, a reaction represented by the following formula (4) is an initiation reaction, followed by a chain reaction represented by the following formulas (5) to (7). It can be considered that chlorine and oxygen are finally produced. Chlorine itself is also known to absorb light with a maximum absorption wavelength of around 3300 nm and an absorption band in the range of about 200 nm to 4500 nm. Yes. At this time, as with chlorine dioxide, it dissociates as shown by the following gel formula (8) to generate radicals, but it is presumed that it becomes chlorine again by the vessel wall or the like.

C 1 O ₂ + h V → CIO * + o * (4)

CIO * + C l ○ 氺 → C 1 2 + ○ ₂ (5)

C 1 O 2 + O * → C 1 0 3 * (6)

2 C 1 O 3 * → C 1 2 0 ₆ → C 1 2 + 3 O ₂ (7)

C 1 2 + hv → CI * + C 1 氺 (8) The photolysis equipment used for photolysis of chlorine oxide has a light irradiator through which chlorine flows and an explosion-proof light source. Should be sealed, purged with air or inert gas, etc., and exhausted to a detoxification line in case of chlorine leakage. O As a 7U irradiation method, an intubation tube is provided in the light irradiator. A light source may be installed in the intubation tube, and light may be emitted from the inside of the light irradiator. Alternatively, a light source may be installed outside the light irradiator and light may be emitted from the outside. . The light irradiator may be in any form, for example, may be a straight tube or a spiral, or may be provided with a plate or the like inside the light irradiator. Also, if necessary, a plurality of light beams and guns may be connected in series or in parallel. Further, the reflection efficiency of light may be improved by using a reflecting mirror around the surroundings. The material of the light irradiator used for the light irradiation may be transparent as long as it is resistant to chlorine and each light source. For example, glass or plastic can be used.

The photodecomposition reaction may be performed in the gas phase or in the liquid phase, but for safety, it is better to irradiate light in the gas phase, and vaporize the raw chlorine in the vaporizer before the photolysis process It is preferable to do so. The photolysis reaction can be carried out either batchwise or flow-through, but a flow-through method is preferred because continuous purification is possible. The light source used for the photodecomposition of chlorine oxide may be light having a wavelength within the range of absorption wavelength of chlorine dioxide,

Wavelengths below 3 3 O nm are strongly affected by absorption by chlorine, so in order to decompose chlorine dioxide, more than one energy absorbed by chlorine is required, and the pressure of chlorine It is not efficient and practical because it is affected. Therefore, as the light source, it is preferable to use a light source having a relatively small absorption of chlorine and having a wavelength within the absorption wavelength range of chlorine dioxide, for example, a wavelength in the range of 300 nm to 500 nm. Therefore, examples of such lamps include various fluorescent lamps, low-pressure mercury lamps, LED lamps, various HID lamps (high-pressure mercury lamps, high-pressure sodium lamps, metal halide lamps, etc.) and the like. A lamp with a wavelength of nm can be used.

In the same light irradiator using the same type of light source with the above-mentioned wavelength range, the time required for photolysis is simply proportional to the chlorine oxide concentration and the light intensity. It can be determined by the type of light, the diameter of the light irradiator, light intensity, chlorine oxide concentration and chlorine flow rate.

The temperature in the photolysis step may be a usual temperature, preferably 20 to 60 ° C. The pressure may be a normal pressure, and is preferably from 0.01 to 1.5 MPa.

The distillation step in the present invention can be carried out by a normal distillation operation. However, it is preferable to carry out distillation that cuts off low-boiling components at an optimum reflux ratio in order to remove oxygen generated in the photolysis step. . This not only removes oxygen but also removes low-boiling point impurities such as nitrogen and hydrogen. Subsequently, heavy metal, water and water are distilled by performing distillation to cut off the high boiling point components at total reflux. Impurities of high boiling point components such as organic substances can also be removed. By using the method of the present invention, continuous purification is possible, and the equipment cost can be kept low.

The present invention will be described with reference to the following examples, but the present invention is not limited to these examples.

FIG. 1 is a schematic diagram showing the steps of the method of the present invention. Raw material chlorine containing chlorine oxide impurities is vaporized by the vaporizer 1 and sent to a photolysis process having a photolysis device 2, where chlorine oxide impurities are removed by photolysis. Subsequently, it is sent to a distillation process having a distillation column 3, where oxygen and other impurities produced by the decomposition of chlorine oxide are distilled off.

Figure 2 shows the photolysis device used in the example, which irradiates light from the inside of the light irradiator. The photolysis device 4 is provided with a stainless steel tube 7, and a glass tube 8 is fixed at the center by a flange 9, packing 10, and screws 1 1, and the glass tube 8 has a lamp. 1 2 is inserted, and gas is introduced from inlet 1 3 and circulated to outlet 1 4. The entire light irradiator is sealed, air and inert gas are introduced through the inlet 5, and the outlet 6 is connected to abatement.

Fig. 3 shows the photolysis device used in the example, which irradiates light from the outside of the light irradiator. Glass tube 1 8 is fixed to photolysis device 1 5 with flange 19, screw 20, screw 2 1, lamp 2 2 is installed around the glass tube, and gas is supplied to inlet 2 3 Introduced from and distributed to outlet 24. The entire light irradiator is sealed, air is inert gas introduced through inlet 16 and outlet 17 is connected to abatement.

Chlorine dioxide is analyzed by Fourier transform infrared spectroscopy, and other impurity gases are analyzed by a gas chromatograph with a TCD detector. More went.

Example 1

According to the process shown in Fig. 1, in the photolysis step 2, three fluorescent lamps (FL 6 WD 6 W from National) are used as lamps in the photolysis device 4 shown in Fig. 2, and chlorine containing chlorine dioxide is used in the photolysis tube. The gas was flowed at a flow rate of 100 NL / min at a pressure of 0. IMP a and IMP a. At this time, the inlet concentration of chlorine dioxide was 20 ppm, but it was less than 0. Olpm at the outlet after photolysis. Thereafter, the low-boiling component and the high-boiling component were removed by distillation, and the chlorine gas was liquefied, filled into a container and analyzed, and the purity was 99.999% or more. Even if the container was left for 30 days and analyzed, the purity was 99.9999% or more.

Example 2

With the process shown in Fig. 1, in the photolysis process, a high-pressure mercury lamp (Sen Special Light Source Co., Ltd. HL— 1 0 0 C H_5, 1 0 0 W) is used as a lamp in the photolysis apparatus 15 shown in FIG. Used, irradiate light only in one direction toward the glass tube 18 and flow chlorine gas containing chlorine dioxide into the photolysis tube at a flow rate of 30 N LZ at a pressure of 0. IMP a and IMP a. I let it pass. The inlet concentration of chlorine dioxide at this time was 10 ppm, but at the outlet after photolysis, it was less than 0.1 ppm. After that, low boiling point components and high boiling point components were removed by distillation, and this chlorine gas was liquefied, filled into a container and analyzed, and the purity was 99.999% or more. Even if the container was left for 30 days and analyzed, the purity was 99.9999% or more.

Example 3

Example 2 except that six fluorescent lamps (FL 6 WD 6 W made by National) were used as the lamps and light was irradiated from six directions around the glass tube. Similar results were obtained when chlorine gas was circulated under the same conditions.

Example 4

A similar result was obtained when chlorine gas was circulated under the same conditions as in Example 2 except that a metal halide lamp (MCK 1 5 0 W-0 7 H 1 5 0 W manufactured by Iwasaki Electric Co., Ltd.) was used as the lamp. Obtained.

Example 5

A low-pressure mercury lamp (manufactured by Sen Special Light Source Co., Ltd. HF—100 G 20 W) was used as the lamp, and chlorine gas was circulated under the same conditions as in Example 2 except that the flow rate was 20 NL / min. However, similar results were obtained. Example 6

Similar results were obtained when black light (NEC FL 15 BL- B 15 W) was used as the lamp and chlorine gas was circulated under the same conditions as in Example 2 except that the flow rate was 20 NL / min. was gotten.

Example 7

Circulating chlorine gas under the same conditions as in Example 2 except that an incandescent bulb (RF 1 0 0 V 2 7 0 WH 2 7 0 W manufactured by Iwasaki Electric Co., Ltd.) was used as the lamp and the flow rate was 20 N LZ. When similar results were obtained, Comparative Example 1

Chlorine gas was purified only by the distillation process without using the photoreaction process. The inlet concentration of chlorine dioxide at this time was 10 ppm, but it was 7 ppm at the outlet of the distillation process, and the amount removed was small. When chlorine was filled in the container and analyzed, chlorine dioxide was 7 ppm, but other impurities including oxygen were 1 ppm or less, and the total impurity concentration was l O p pm or less. Yes, the purity was 9 9. 9 9 9% or more . However, when this vessel was left for 30 days and its gas phase was analyzed, chlorine dioxide decreased to 4 ppm, oxygen increased to 700 ppm, and the purity of chlorine decreased. This is because chlorine dioxide is gradually decomposed in the container, and oxygen produced by the decomposition of chlorine dioxide is concentrated on the gas phase side, so that the oxygen impurity concentration increases and the purity of chlorine gas decreases, and high-purity applications It has become unsuitable for.

The above results are summarized in Table 1.

Photolysis process Niic acid 'Sodium chloride concentration (m) Chlorine purity (%) Pressure (MPa) Before purification 30 days after filling After 30 days after filling Example 1 0. 1 20 <0. 01 <0. 01> 99 999> 99. 999

1. 0 20 <0. 01 <0. 01> 99. 999> 99. 999 Example 2 0. 1 10 <0. 01 <0. 01> 99. 999> 99. 999

1. 0 10 <0. 01 <0. 01> 99. 999> 99. 999 Example 3 0. 1 10 <0. 01 right 0. 01> 99. 999> 99. 999

1. 0 10 <0. 01 <0. 01> 99. 999> 99. 999 Example 4 0. 1 10 <0. 01 <0. 01> 99. 999> 99. 999

1. 0 10 <0. 01 <0. 01> 99. 999> 99. 999 Example 5 0. 1 10 <0. 01 <0. 01> 99. 999> 99. 999

1. 0 10 <0. 01 <0. 01> 99.999> 99.999 Example 6 0.1.10 <0.01 <0.01> 99.999> 99.999

1. 0 10 <0. 01 <0. 01> 99. 999> 99. 999 Example 7 0. 1 10 <0. 01 <0. 01> 99. 999> 99. 999

1. 0 10 <0. 01 <0. 01> 99. 999> 99. 999 Comparative Example 1 1 10 7 4> 99. 999 99. 93

Industrial applicability

INDUSTRIAL APPLICABILITY According to the present invention, chlorine oxide in chlorine can be easily and economically and efficiently removed to produce high-purity liquefied chlorine, which can be advantageously used industrially.

Claims

1. In a method for producing high-purity liquefied chlorine by refining raw material chlorine containing chlorine oxide as an impurity, the raw material chlorine is irradiated with light and the chlorine oxide impurity is converted into chlorine and oxygen by photolysis. Photolysis process to decompose, and photolysis products and other impurities are removed by distillation

A method for producing high-purity liquefied chlorine, comprising a distillation step.

2. The method for producing high-purity liquefied chlorine according to claim 1, wherein the concentration of chlorine oxide impurities is 0.1 to 50 ppm.

3. The method for producing high-purity liquefied chlorine according to claim 1 or 2, wherein the chlorine oxide impurity is chlorine dioxide.

Surrounding

4. The method for producing high-purity liquefied chlorine according to any one of claims 1 to 3, wherein the light source in the photolysis step is a light source including a wavelength in the range of 300 to 500 nm.

5. The method for producing high-purity liquefied chlorine according to any one of claims 1 to 4, wherein the raw material chlorine is vaporized by a vaporizer before the photolysis step, and the photolysis reaction is performed in the gas phase in the photolysis step.

6. The method for producing high-purity liquefied chlorine according to any one of claims 1 to 5, wherein the photolysis reaction in the photolysis step is a flow-type photolysis reaction.

7. The method for producing high-purity liquefied chlorine according to any one of claims 1 to 6, wherein the temperature of the photolysis reaction in the photolysis step is 20 to 60 ° C.

8. The method for producing high-purity liquefied chlorine according to any one of claims 1 to 7, wherein the pressure of the photolysis reaction in the photolysis step is 0.01 to 1.5 MPa.

9. The high-purity liquefied chlorine according to claim 1, wherein the distillation step includes a low-boiling distillation step for removing low-boiling impurities including oxygen generated in the photolysis step. Manufacturing method.

10. The method for producing high-purity liquefied chlorine according to any one of claims 1 to 9, wherein the purity of the high-purity liquefied chlorine is 99.999% or more.