Liquid chlorine storage material

Abstract

This invention provides a liquid chlorine storage material for separating and storing chlorine from chlorine-containing gases. The material is a mixed ionic liquid composed of at least one organic salt and one additive, wherein the organic salt is selected from one or more quaternary ammonium salts, and the additive is a metal chloride. The chlorine storage material is liquid at 25°C and a pressure of 1000±100 hPa. This invention provides a storage medium with a high chlorine storage rate, high chlorine storage density, simple release conditions, and high chlorine purity. This storage medium effectively reduces the saturated vapor pressure of chlorine at room temperature, improving the safety of chlorine transportation and use.

Description

Technical Field

[0001] This invention relates to the field of chlorine storage, and more particularly to a liquid chlorine storage material. Background Technology

[0002] In the industrial production and use of chlorine, chlorine is typically liquefied to purify, recover, and transport it. In chlorine production, liquefaction is used to separate impurity gases such as oxygen, nitrogen, or carbon dioxide. These gases have lower boiling points than chlorine and can therefore be separated as gaseous phases through chlorine liquefaction. In industrial applications, chlorine generally needs to be liquefied before being transported via pipelines or roads. Chlorine can be liquefied at high pressures of 7 bar or low temperatures of around -35°C. This process requires a significant amount of energy, resulting in high costs for chlorine storage and transportation.

[0003] To withstand high pressure, the walls of compressed gas cylinders and pipelines used for storing and transporting chlorine are typically very thick, resulting in higher production and transportation costs. Furthermore, chlorine gas in the compressed cylinders must be released through a pressure regulator, which must be tightly sealed to the cylinder and equipment to prevent chlorine escape and potential hazards. Due to the corrosive and toxic nature of chlorine, the transportation of cylinders and the release of chlorine gas must be carried out under special safety precautions.

[0004] Existing technologies disclose storage media for chlorine absorption based on physical adsorption. However, the chlorine mass storage density of such storage materials is very low because there is only a physical interaction between the porous solid and the chlorine. For example, US5376164A1 discloses the adsorption of chlorine on various zeolites and silica gels, where only 0.2 g of chlorine can be adsorbed per gram of storage material at room temperature and 0.87 bar.

[0005] Ionic compounds composed of certain organic cations and chlorides have a high affinity for chlorine gas and can bind chlorine in the form of polychlorinated ions. WO2007109611A1 discloses a medium for the safe storage and transportation of chlorine gas under ambient pressure, preferably 1-methyl-3-ethylimidazolium chloride and pyridinium hydrochloride. However, this medium is solid at room temperature, which limits its application in filling and transportation.

[0006] EP18170956.9 discloses a method based on the general formula N-R1 m R2 n R3 o + Cl r - Or P-R4 p R5 q + Cl s -Ionic compounds are used as reversible chlorine storage media, with R1 and other groups selected from alkyl groups with 5 or fewer carbon atoms. However, the preferred trimethylethylammonium chloride, dimethyldiethylammonium chloride, and methyltriethylammonium chloride are all solids at room temperature, which limits their flexibility in filling and transportation.

[0007] The current technical problem is that existing chlorine storage media are solid or high-viscosity liquids at room temperature, and have low mass storage density, making them inconvenient for chlorine absorption and filling and transportation.

[0008] Therefore, it is indeed necessary to provide an improved chlorine storage medium to overcome the problems existing in current chlorine storage materials. Summary of the Invention

[0009] The present invention provides a liquid chlorine storage material for separating and storing chlorine from chlorine-containing gases. The medium is a mixed ionic liquid composed of at least one organic salt and an additive, wherein the organic salt is selected from one or more quaternary ammonium salts, and the additive is a metal chloride. The liquid chlorine storage material is liquid at a temperature of 25°C and a pressure of 1000±100 hPa.

[0010] Preferably, the metal chloride is selected from one or more of aluminum chloride, nickel chloride, magnesium chloride, and lithium chloride.

[0011] The core nitrogen atom in quaternary ammonium salts has high electronegativity, and even after forming a complex, it still strongly attracts chlorine gas, forming polychlorinated complexes (PCCs), i.e., PCC quaternary ammonium salts, thus suitable for chlorine storage. However, quaternary ammonium salts that combine with chlorine to form PCCs are usually solids or highly viscous liquids at room temperature, which is inconvenient for their application in chlorine storage media, and the reaction rate for storing chlorine is relatively slow. In contrast, metal chlorides partially dissociate into metal ions and chloride ions during dissolution in ionic liquids. This process effectively increases the conductivity of the ionic liquid, but also slightly increases its viscosity. Some chloride ions can fully contact the quaternary ammonium salt in the liquid phase to form PCC compounds. Chlorine gas exists simultaneously in the ionic liquid in both molecular and ionic forms, interconverting to achieve a dynamic equilibrium between chlorine consumption and generation. Therefore, the initial chlorine storage rate of this storage medium is relatively fast.

[0012] Preferably, the metal chloride is lithium chloride.

[0013] Lithium, with its lightweight, high energy density, and easy recharging properties, is one of the most suitable polar elements for battery manufacturing. Lithium chloride has a sodium chloride-type structure, and its chemical bonds are not typical ionic bonds. Therefore, it is soluble in many organic solvents and can form adducts with ethanol, methanol, and amines of varying compositions. Due to lithium's small ionic radius and high hydration energy, lithium chloride has a much higher solubility than other chlorides in the same group. Therefore, lithium chloride can rapidly dissolve and dissociate into chloride and lithium ions in quaternary ammonium salt ionic liquids, a process that effectively increases the conductivity of the ionic liquid.

[0014] Preferably, the mass fraction of the additive lithium chloride is 5% to 20%.

[0015] Preferably, the mass fraction of the additive lithium chloride is 10%.

[0016] Preferably, the substituent group in the quaternary ammonium salt is an alkyl group with 1 to 5 carbon atoms in the main chain.

[0017] Preferably, the anion in the quaternary ammonium salt is selected from one or more of chloride ions, bromide ions, iodide ions, fluoride ions, sulfate ions, and acetate ions.

[0018] Preferably, the quaternary ammonium salt is methyltrioctylammonium chloride.

[0019] Methyltrioctylammonium chloride has a melting point of -20°C and is a liquid at room temperature. The nitrogen atom in this compound consists of straight-chain alkyl groups with minimal steric hindrance, which facilitates the rapid attack of dissolved chlorine gas on ammonium ions in ionic form. This process converts the chlorine gas into polychlorinated compounds (such as [NEt3Me]Cl). 3.5.7.9 ) is stored in the form of ) to effectively reduce the saturated vapor pressure of chlorine.

[0020] In one embodiment, chlorine is released by heating a chlorine-loaded storage medium. The polychlorinated compounds in the storage medium are unstable; heating intensifies their molecular thermal motion, causing chloride ions to recombine into chlorine molecules that escape. The inorganic salts and ionic liquids used in this storage medium have extremely low saturated vapor pressures at 60°C and are stable, thus preventing the release of other gases and ensuring the purity of the chlorine.

[0021] In one embodiment, chlorine is released by depressurizing a chlorine-loaded storage medium. The polychlorinated compounds in the storage medium exist in ionic form, and a dynamic equilibrium of various ions and molecules exists within the ionic liquid. After depressurization, the solubility of chlorine in the ionic liquid decreases, and chloride ions recombine to form chlorine molecules that escape. As the amount of chlorine in the ionic liquid decreases, the polychlorinated compounds tend to decompose into monochloride salts and chloride ions. The inorganic salts and ionic liquids used in this storage medium have extremely low saturated vapor pressures at room temperature and are stable, thus preventing the release of other gases and ensuring the purity of the chlorine.

[0022] In one embodiment, chlorine is released by purging a chlorine-loaded storage medium with a purge gas. The purge gas, referred to as the carrier gas, contains no chlorine or contains very little chlorine, causing the chlorine to transfer from the liquid phase to the gas phase, thereby carrying the chlorine out of the storage medium. The carrier gas is selected from air, nitrogen, carbon dioxide, water vapor, etc., preferably an inert gas. In one embodiment, the chlorine-loaded storage medium is sprayed down from the top of a desorption tower, and the carrier gas comes into countercurrent contact with the storage medium from the bottom of the desorption tower, carrying the chlorine out and releasing it. In another embodiment, inert nitrogen gas is introduced into the chlorine-loaded storage medium, and the mixed gas above the storage medium is collected through an exhaust pipe and transported to a reactor. The controlled release of chlorine can be achieved by controlling the flow rate of the nitrogen gas.

[0023] The aforementioned storage medium can be used to separate chlorine from chlorine-containing process gases, particularly from process gases containing H2, CO2, O2, CO, NO, NO2, N2O4, SO2, SO3, SO, S2O2, SO4, and mixtures thereof. Chlorine can be separated from the gas mixture by ensuring sufficient contact between the chlorine-containing process gas and the storage medium. The contact between the storage medium and the chlorine-containing gas can, in principle, be carried out in any known gas-liquid absorption device, such as a packed tower or plate tower. After chlorine absorption, the storage medium accumulates at the bottom of the container and can continue to absorb or be discharged in liquid form. The chlorine-free impurity gases, after separation, accumulate in the upper gas phase and can be easily separated.

[0024] The beneficial effects of this invention are: ① This storage medium is a low-viscosity liquid in the working environment, which not only has a high chlorine storage rate and a large chlorine storage density per unit mass, but is also suitable for use in liquid filling, pipeline transportation, etc. ② This storage medium effectively reduces the saturated vapor pressure of chlorine at room temperature, improving the safety of chlorine transportation and use. In the event of an accidental leak, the release rate of chlorine from the storage medium is very low, effectively reducing the risk of chlorine posing a threat to environmental safety. ③ The chlorine gas released from this storage medium is easy and of high purity. Chlorine can be released and utilized in a controlled manner by heating the chlorine-loaded storage medium, reducing its partial pressure, or purging with gas. The vapor pressure of this storage medium is extremely low, preventing it from entering the gas phase; therefore, the released chlorine gas is of high purity.

[0025] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following lists specific embodiments of this application.

[0026] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0027] Figure 1 Viscosity relationships of ionic liquids prepared in different embodiments.

[0028] Figure 2 A graph showing the relationship between the mass chlorine storage density of ionic liquids prepared in different embodiments. Detailed Implementation Example

[0029] Methyltrioctylammonium chloride (202.08 g) and aluminum chloride (10.10 g) were added to a flask at 25 °C and stirred thoroughly to dissolve into an ionic liquid, thus preparing a liquid chlorine storage material. Example

[0030] Methyltrioctylammonium chloride (202.08 g) and nickel chloride (10.10 g) were added to a flask at 25 °C and stirred thoroughly to dissolve into an ionic liquid, thus preparing a liquid chlorine storage material. Example

[0031] Methyltrioctylammonium chloride (202.08 g) and magnesium chloride (10.10 g) were added to a flask at 25 °C and stirred thoroughly to dissolve into an ionic liquid, thus preparing a liquid chlorine storage material. Example

[0032] Methyltrioctylammonium chloride (202.08 g) and lithium chloride (10.10 g) were added to a flask at 25 °C and stirred thoroughly to dissolve into an ionic liquid, thus preparing a liquid chlorine storage material. Example

[0033] Methyltrioctylammonium chloride (202.08 g) and lithium chloride (20.21 g) were added to a flask at 25 °C and stirred thoroughly to dissolve into an ionic liquid, thus preparing a liquid chlorine storage material. Example

[0034] Methyltrioctylammonium chloride (202.08 g) and lithium chloride (30.31 g) were added to a flask at 25 °C and stirred thoroughly to dissolve into an ionic liquid, thus preparing a liquid chlorine storage material. Example

[0035] Methyltrioctylammonium chloride (202.08 g) and lithium chloride (40.42 g) were added to a flask at 25 °C and stirred thoroughly to dissolve into an ionic liquid, thus preparing a liquid chlorine storage material.

[0036] Comparative Example 1 202.08 g of methyltrioctylammonium chloride was added to a flask at 25°C without adding any other substances.

[0037] The viscosities of the ionic liquids prepared in all the above examples were measured using a micro Ubbelohde viscometer at 25°C and 1000 hPa. The ionic liquids were placed in flasks, and dry chlorine gas was introduced at 1000 hPa until the overall mass of the flask no longer increased. The difference in the overall mass of the flask before and after the introduction of chlorine gas is taken as the mass of chlorine absorbed, m0. The initial mass of the ionic liquid is recorded as m1. The chlorine mass absorption density of the ionic liquid is then μ = m0 / m1 * 100%. The measured viscosities and chlorine mass absorption densities are recorded in Table 1. Comparing the various embodiments with the chlorine storage medium based solely on triethylmethylammonium chloride in Comparative Example 1, it can be seen that after the quaternary ammonium salt ionic liquid is prepared by adding metal chloride additives, the metal chloride dissociates into metal ions and chloride ions, the overall viscosity of the solution increases slightly, and the conductivity increases significantly, which is more conducive to the absorption of chlorine gas. The mass chlorine storage density in each embodiment reaches as high as 13.4%.

[0038] A comparison of the viscosity and mass chlorine storage density of the chlorine storage media prepared in Examples 1-4 shows that, with the same mass of additives, lithium chloride exhibits the best performance, while the ionic liquid has the lowest relative viscosity and the highest chlorine storage density. This is presumably because lithium has a small ionic radius and low atomic mass, and lithium chloride has a sodium chloride-type structure where the chemical bonds are not typical ionic bonds. It can dissolve in organic solvents and form adducts with amines of different compositions, resulting in significantly higher solubility and dissolution rate compared to other chlorides. Lithium chloride can rapidly dissolve and dissociate into chloride and lithium ions in quaternary ammonium salt ionic liquids. This process effectively increases the conductivity of the ionic liquid and enhances the polarity of the quaternary ammonium salt. When chlorine gas passes through, it is more easily adsorbed and condenses with the quaternary ammonium salt to form polychlorinated quaternary ammonium salts, such as [NEt3Me]Cl. 3.5.7.9 wait.

[0039] Comparing the viscosity and mass chlorine storage density of the chlorine storage media prepared in Examples 4-7 and Comparative Example 1, it can be seen that the viscosity of the ionic liquid increases with increasing lithium chloride concentration, while the mass chlorine storage density initially increases with increasing lithium chloride concentration, and then decreases with further increases in concentration. It is speculated that when the viscosity is low, the conductivity of the ionic liquid increases with increasing additive concentration, which is beneficial for the adsorption of chlorine molecules. Since the viscosity increases with increasing additive concentration, when the viscosity is too high, the dissolution and absorption of chlorine by the ionic liquid are significantly hindered, thus the mass chlorine storage density initially increases and then decreases.

[0040] This storage medium is a low-viscosity liquid under operating conditions, which not only provides high chlorine storage speed and density, but also simplifies release conditions and ensures high chlorine purity. This storage medium effectively reduces the saturated vapor pressure of chlorine at room temperature, improving the safety of chlorine transportation and use.

[0041] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions conceived without inventive effort should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A liquid chlorine storage material, characterized in that, It is a mixed ionic liquid composed of at least one organic salt and one additive, wherein the organic salt is selected from one or more quaternary ammonium salts, and the additive is a metal chloride. The liquid chlorine storage material is liquid at a temperature of 25°C and a pressure of 1000±100hPa.

2. The liquid chlorine storage material as described in claim 1, characterized in that, The metal chloride is selected from one or more of aluminum chloride, nickel chloride, magnesium chloride, and lithium chloride.

3. The liquid chlorine storage material as described in claim 2, characterized in that, The metal chloride is lithium chloride.

4. The liquid chlorine storage material as described in claim 3, characterized in that, The mass fraction of the additive is 5% to 20%.

5. The liquid chlorine storage material as described in claim 4, characterized in that, The additive has a mass fraction of 10%.

6. The liquid chlorine storage material as described in claim 1, characterized in that, The substituent groups in the quaternary ammonium salt are alkyl groups with 1 to 5 carbon atoms in the main chain.

7. The liquid chlorine storage material as described in claim 6, characterized in that, The anion in the quaternary ammonium salt is selected from one or more of chloride ions, bromide ions, iodide ions, fluoride ions, sulfate ions, and acetate ions.

8. The liquid chlorine storage material as described in claim 7, characterized in that, The quaternary ammonium salt is methyltrioctylammonium chloride.

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