Method for purifying bromine gas

Abstract

Provided is a method for purifying a bromine gas, the method being capable of selectively removing chlorine molecules from the bromine gas. The method for purifying a bromine gas comprises a purification step for bringing a chlorine-removing agent, which has a metal bromide supported on an adsorbent, into contact with the bromine gas to remove, from the bromine gas, chlorine molecules contained in the bromine gas.

Description

Method for purifying bromine gas

[0001] The present disclosure relates to a method for purifying bromine gas.

[0002] Industrially produced bromine gas (Br) usually contains chlorine molecules (Cl) as an impurity. Therefore, methods for purifying bromine gas by removing chlorine molecules from bromine gas have been proposed. For example, Patent Document 1 proposes a halogen gas remover containing a sulfur-containing reducing agent such as thiosulfate and pseudoboehmite.

[0003] Japanese Patent Publication No. 6975537

[0004] According to the technology disclosed in Patent Document 1, it is possible to fix chlorine molecules in bromine gas to a halogen gas removing agent and remove them, but there is a risk that bromine gas may also be fixed to the halogen gas removing agent and removed. Therefore, there has been a need for a technology for purifying bromine gas by selectively removing chlorine molecules from bromine gas. An object of the present disclosure is to provide a method for purifying bromine gas that can selectively remove chlorine molecules from bromine gas.

[0005] In order to solve the above problems, one aspect of the present disclosure is as follows: [1] to [6]. [1] A method for purifying bromine gas, comprising a purification step of contacting bromine gas with a chlorine-removing agent comprising an adsorbent supported with a metal bromide, thereby removing chlorine molecules contained in the bromine gas from the bromine gas.

[0006] [2] The method for purifying bromine gas according to [1], wherein the adsorbent comprises at least one of activated alumina and zeolite. [3] The specific surface area of ​​the chlorine-removing agent is 100 m 2 [4] The method for purifying bromine gas according to any one of [1] to [3], wherein the average particle size of the chlorine-removing agent is in the range of 0.5 mm to 10 mm.

[0007] [5] The method for purifying bromine gas according to any one of [1] to [4], wherein the metal bromide comprises at least one of potassium bromide, sodium bromide, calcium bromide, and magnesium bromide. [6] The method for purifying bromine gas according to any one of [1] to [5], wherein the content of the metal bromide in the chlorine-removing agent is 1% by mass or more and 50% by mass or less.

[0008] According to the method for purifying bromine gas according to the present disclosure, it is possible to selectively remove chlorine molecules from bromine gas.

[0009] An embodiment of the present disclosure will be described below. Note that this embodiment shows an example of the present disclosure, and the present disclosure is not limited to this embodiment. Furthermore, various modifications or improvements can be made to this embodiment, and such modifications or improvements may also be included in the present disclosure.

[0010] The method for purifying bromine gas according to this embodiment includes a purification step of contacting bromine gas with a chlorine-removing agent comprising an adsorbent supported on a metal bromide, thereby removing chlorine molecules contained as impurities in the bromine gas from the bromine gas. That is, the method for purifying bromine gas according to this embodiment includes a purification step of contacting bromine gas with a chlorine-removing agent comprising an adsorbent supported on a metal bromide, thereby removing chlorine molecules from the bromine gas.

[0011] With the above-described configuration, it is possible to selectively adsorb and remove chlorine molecules from bromine gas while suppressing adsorption of bromine gas to the chlorine-removing agent, and therefore, the method for purifying bromine gas according to this embodiment is simple and economical, requiring low equipment costs.

[0012] [Adsorbent] The type of adsorbent used in the bromine gas purification method according to this embodiment is not particularly limited as long as it has high adsorption properties and an average particle size that can be used as a raw material for a chlorine remover, and examples thereof include activated alumina and zeolite (natural zeolite and synthetic zeolite). That is, the adsorbent may contain at least one of activated alumina and zeolite. Note that at least one of activated alumina and zeolite may be used alone as the adsorbent, or at least one of activated alumina and zeolite may be used in combination with another type of adsorbent.

[0013] [Metal Bromide] The type of metal bromide used in the bromine gas purification method according to this embodiment is not particularly limited as long as it functions as a component for reacting with and fixing chlorine molecules, and examples thereof include alkali metal bromides and alkaline earth metal bromides. Examples of alkali metal bromides include potassium bromide (KBr), sodium bromide (NaBr), calcium bromide (CaBr), and magnesium bromide (MgBr). Among these, potassium bromide and sodium bromide are preferred. That is, the metal bromide may include at least one of potassium bromide, sodium bromide, calcium bromide, and magnesium bromide.

[0014] The metal bromide may be potassium bromide, sodium bromide, calcium bromide, or magnesium bromide, either singly or in combination. The metal bromide may be an alkali metal bromide alone or in combination with another metal bromide.

[0015] [Chlorine Removal Agent] The chlorine removal agent in the bromine gas purification method according to this embodiment is an adsorbent having a metal bromide supported thereon (for example, an adsorbent having a metal bromide supported on its surface). Use of a chlorine removal agent obtained by supporting a metal bromide on an adsorbent makes it possible to selectively remove chlorine molecules while suppressing adsorption of bromine gas.

[0016] That is, when an adsorbent not supporting metal bromide is used as a chlorine removing agent, not only chlorine molecules but also bromine molecules are adsorbed in the pores of the chlorine removing agent, resulting in the removal of bromine gas. However, when a chlorine removing agent supporting metal bromide is used, the metal bromide is supported in the pores, so that the adsorption of bromine molecules is physically suppressed compared to an adsorbent not supporting metal bromide, and chlorine molecules can be selectively fixed to the chlorine removing agent by a chemical oxidation-reduction reaction in addition to adsorption. The chlorine molecules are fixed, for example, on the surface of the chlorine removing agent.

[0017] Furthermore, the chlorine removing agent in the method for purifying bromine gas according to this embodiment has a high chlorine removal rate, expressed as the ratio of the outlet concentration to the inlet concentration of chlorine molecules in the bromine gas that has flowed through the chlorine removing agent until breakthrough. This is presumably because, when an adsorbent that does not support a metal bromide is used as the chlorine removing agent, some of the adsorbed chlorine molecules are released into the outlet gas by desorption, whereas when the chlorine removing agent in the method for purifying bromine gas according to this embodiment is used, the chlorine molecules are immobilized as described above and are therefore less likely to desorb.

[0018] The content of metal bromide in the chlorine removing agent is not particularly limited, but may be, for example, 1% by mass or more and 50% by mass or less. The content of metal bromide in the chlorine removing agent is preferably 1% by mass or more and 50% by mass or less, and more preferably 5% by mass or more and 20% by mass or less. When the content of metal bromide in the chlorine removing agent is within the above range, the amount of chlorine molecules that can be removed tends to increase, and in addition, the specific surface area of ​​the chlorine removing agent is sufficient, so that the amount of chlorine molecules removed tends to increase in proportion to the content of metal bromide in the chlorine removing agent.

[0019] The content of metal bromide in the chlorine removing agent can be calculated by the following formula: (W2 - W1) / W2 × 100 (mass%) In the above formula, W1 is the mass of the adsorbent, and W2 is the mass of the chlorine removing agent. An example of a method for producing a chlorine removing agent in the method for purifying bromine gas according to this embodiment is shown below. The chlorine removing agent can be obtained by immersing an adsorbent in a solution of metal bromide (e.g., an aqueous potassium bromide solution) and leaving it for a predetermined time, and then removing the adsorbent from the metal bromide solution and drying it.

[0020] The shape of the chlorine removing agent is not particularly limited, and may be, for example, pellet-like, tablet-like, or spherical, and is particularly preferably porous. The specific surface area of ​​the chlorine removing agent is not particularly limited, but from the viewpoint of suppressing the adsorption of bromine gas and maintaining the physical strength of the particles of the chlorine removing agent, the specific surface area of ​​the chlorine removing agent is preferably 100 m 2 / g or more is preferred.

[0021] The average particle size of the chlorine removing agent is not particularly limited, but is preferably in the range of 0.5 mm to 10 mm, and more preferably in the range of 1 mm to 5 mm. The larger the average particle size of the chlorine removing agent, the smaller the surface area involved in the adsorption and diffusion of bromine gas, and therefore the slower the diffusion rate of bromine gas. However, if the average particle size of the chlorine removing agent is within the above range, the diffusion rate of bromine gas is likely to be favorable. Furthermore, the smaller the average particle size of the chlorine removing agent, the larger the surface area involved in the adsorption and diffusion, and therefore the faster the diffusion rate of bromine gas itself. However, as the amount of bromine gas to be treated increases, the differential pressure between the inlet and outlet of the removal column filled with the chlorine removing agent and into which bromine gas is introduced to purify the bromine gas increases. However, as the average particle size of the chlorine removing agent is within the above range, the differential pressure between the inlet and outlet of the removal column for purifying bromine gas is likely to be in the favorable range, even if the amount of bromine gas to be treated increases.

[0022] [Method for Purifying Bromine Gas] An example of a method for purifying bromine gas according to the present embodiment is shown below. The bromine gas can be purified by passing bromine gas through a cylindrical removal tube filled with a chlorine-removing agent in a purification step, whereby chlorine molecules contained in the bromine gas are adsorbed onto the chlorine-removing agent.

[0023] The temperature at which bromine gas is purified is not particularly limited, but is preferably 80° C. or higher. The concentration of chlorine molecules contained in the bromine gas is not particularly limited, but is preferably 200 ppm by mass or less. When the concentration of chlorine molecules contained in the bromine gas exceeds 200 ppm by mass, the concentration of chlorine molecules contained in the bromine gas may be reduced to 200 ppm by mass or less by a method such as distillation separation or condensation separation, and then the bromine gas may be purified by the bromine gas purification method according to this embodiment.

[0024] The present disclosure will be described in more detail below with reference to examples and comparative examples. Example 1: Activated alumina NST-3 (specific surface area 156 m) manufactured by Nikki-Universal Co., Ltd. 2 / g, average particle size 4.0 mm) was used as an adsorbent to produce a chlorine remover. The specific surface area was measured by the BET method. The average particle size was measured by an image processing method.

[0025] 100 g of the adsorbent was placed in 200 mL of a 15% by mass aqueous potassium bromide solution and immersed for 30 minutes to allow the adsorbent to absorb the potassium bromide solution. The adsorbent was then removed from the aqueous potassium bromide solution and dried for 3 hours in a dryer at 150°C to obtain a chlorine-removing agent. The metal bromide (potassium bromide) content (KBr loading) in the obtained chlorine-removing agent was 20% by mass.

[0026] Bromine gas was purified using the obtained chlorine removing agent. A removal tube was manufactured by filling 20 g of the chlorine removing agent into a glass tube with an inner diameter of 15 mm. Bromine gas was introduced into the inlet at one end of the removal tube, and after contacting the bromine gas with the chlorine removing agent, it was discharged from the outlet at the other end of the removal tube. The concentration of chlorine molecules contained in the bromine gas introduced into the removal tube (inlet concentration) was 100 mass ppm. The rate at which the bromine gas was introduced into the removal tube was 100 mL / min. The temperature at which the bromine gas was purified (i.e., the temperature inside the removal tube) was 100°C, and the pressure (i.e., the pressure inside the removal tube) was 0.2 MPa. The 100 mL / min rate at which the bromine gas was introduced into the removal tube was measured at a temperature of 100°C and a pressure of 0.2 MPa.

[0027] The mass of the chlorine removing agent was measured before and after purification. The change in mass was considered to be due to the adsorption of bromine gas by the chlorine removing agent, and is shown in Table 1 as the bromine adsorption amount. The bromine adsorption amount shown in Table 1 is the amount of bromine gas adsorbed per 1 kg of the chlorine removing agent (unit: g). As can be seen from the results shown in Table 1, the chlorine removing agent of Example 1 suppressed the adsorption of bromine gas.

[0028] Bromine gas discharged from the outlet of the removal column was sampled, and the concentration of chlorine molecules contained in the bromine gas (outlet concentration) was measured. The chlorine molecular concentration was measured by ion chromatography. The chlorine removal rate was calculated for the total amount of bromine gas that had flowed until the chlorine removal agent broke through. This chlorine removal rate was calculated using the value (outlet concentration / inlet concentration) obtained by dividing the outlet concentration by the inlet concentration. The results are shown in Table 1.

[0029] Furthermore, the total amount of chlorine molecules adsorbed by the chlorine removing agent (amount of chlorine removed) was calculated from the start of purification until the concentration of chlorine molecules in the outlet gas reached 20 ppm by mass. The results are shown in Table 1. The amount of chlorine removed shown in Table 1 is the amount of chlorine molecules adsorbed per kg of chlorine removing agent (unit: L, a value at room temperature and normal pressure). As can be seen from the results shown in Table 1, the chlorine removing agent of Example 1 had a high ability to remove chlorine molecules.

[0030]

[0031] Example 2 Zeolite CLR-454 (specific surface area 409 m) manufactured by Resonac Universal Co., Ltd. 2 A chlorine remover was produced using a potassium bromide solution (20 g, average particle size 2.3 mm) as an adsorbent. 20 g of the adsorbent was added to 200 mL of a 35% by mass aqueous potassium bromide solution and immersed for 30 minutes to allow the adsorbent to absorb the potassium bromide aqueous solution. The adsorbent was then removed from the potassium bromide aqueous solution and dried for 3 hours in a dryer at 150°C to obtain a chlorine remover. The metal bromide (potassium bromide) content in the obtained chlorine remover was 20% by mass.

[0032] Except for the above points, bromine gas was purified in the same manner as in Example 1, and the bromine adsorption amount, chlorine removal rate, and chlorine removal amount were calculated. The results are shown in Table 1. As can be seen from the results shown in Table 1, the chlorine removing agent of Example 2 adsorbed a small amount of bromine gas and had a high ability to remove chlorine molecules.

[0033] Example 3 Bromine gas was purified in the same manner as in Example 1, except that the potassium bromide content was 0.1% by mass, and the bromine adsorption amount, chlorine removal rate, and chlorine removal amount were calculated. The results are shown in Table 1. As can be seen from the results shown in Table 1, the chlorine removing agent of Example 3 had a larger bromine adsorption amount and a smaller chlorine removal amount than Example 1 because the amount of potassium bromide supported was smaller.

[0034] Comparative Example 1 Bromine gas was purified in the same manner as in Example 1, except that activated alumina not supporting potassium bromide was used as a chlorine-removing agent, and the bromine adsorption amount, chlorine removal rate, and chlorine removal amount were calculated. The results are shown in Table 1.

[0035] As can be seen from the results shown in Table 1, the chlorine removing agent of Comparative Example 1 did not support potassium bromide, and therefore adsorbed a large amount of bromine gas and had a low chlorine removal rate. In addition, the concentration of chlorine molecules in the outlet gas reached 20 ppm by mass more quickly than in Example 1, and therefore the amount of chlorine removed was small.

[0036] Comparative Example 2 Bromine gas was purified in the same manner as in Example 2, except that zeolite not supporting potassium bromide was used as it was as a chlorine removing agent, and the bromine adsorption amount, chlorine removal rate, and chlorine removal amount were calculated. The results are shown in Table 1. As can be seen from the results shown in Table 1, the chlorine removing agent of Comparative Example 2 had a low chlorine removal rate because potassium bromide was not supported. In addition, the concentration of chlorine molecules in the outlet gas reached 20 ppm by mass more quickly than in Example 2, and therefore the amount of chlorine removed was small.

Claims

1. A method for purifying bromine gas, comprising a purification step of contacting bromine gas with a chlorine remover comprising an adsorbent carrying a metal bromide, to remove chlorine molecules contained in the bromine gas from the bromine gas.

2. The method for purifying bromine gas according to claim 1, wherein said adsorbent comprises at least one of activated alumina and zeolite.

3. The specific surface area of ​​the chlorine remover is 100 m 2 3. The method for purifying bromine gas according to claim 1 or 2, wherein the bromine content is 1 / g or more.

4. A method for purifying bromine gas according to claim 1 or 2, wherein the average particle size of the chlorine remover is within the range of 0.5 mm to 10 mm.

5. A method for purifying bromine gas according to claim 1 or 2, wherein the metal bromide comprises at least one of potassium bromide, sodium bromide, calcium bromide, and magnesium bromide.

6. A method for purifying bromine gas according to claim 1 or 2, wherein the content of said metal bromide in said chlorine removing agent is 1% by mass or more and 50% by mass or less.

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