Preparation method of chlorine

Abstract

The invention relates to a preparation method of chlorine, which comprises the following steps: mixing hydrogen chloride, nitrogen oxide and oxygen-containing gas in a light-transmitting reaction container, and sealing; carrying out oxidation reaction under normal pressure and illumination conditions to generate chlorine; wherein the illumination condition is sunlight or a simulated light source, the reaction temperature is 0-100 DEG C, the nitrogen oxide is a catalyst, and in the reaction process, the nitrogen oxide catalyst is excited by light energy to activate oxygen and form a free radical reaction to realize oxidation of hydrogen chloride. Compared with the prior art, the method has the advantages that the impurity-containing hydrogen chloride can be efficiently treated by using nitrogen oxide under normal pressure through a photocatalysis mechanism, high temperature and noble metal catalysts are not needed, the cost is remarkably reduced, the compatibility is improved, the bottleneck of the prior art is broken through, and the industrialization process of preparing chlorine from hydrogen chloride is powerfully promoted.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical production, and particularly relates to a preparation method of chlorine. BACKGROUND

[0002] Chlorine is an important chemical raw material, and plays an important role in the production of inorganic materials, metal oxides, silicon-based materials and organic chlorides. Hydrogen chloride is an inevitable by-product in the industrial production of chlorine-containing compounds, and is derived from the decomposition of hydrochloride, the substitution of organic chlorides and the removal of polymer monomers. The amount of hydrogen chloride generated in industry is much larger than the market demand for hydrogen chloride, and the generated hydrogen chloride is usually absorbed by water to become hydrochloric acid, which is neutralized by alkali as waste water. Such treatment method is a great waste of hydrogen chloride resources. Therefore, the oxidation of hydrogen chloride to chlorine is an important resource recovery technology. The recovery of hydrogen chloride needs to face the complex chemical environment in industrial emissions, and the reaction environment containing water, sulfur and fluorine makes it necessary to have stronger compatibility when preparing chlorine from recovered hydrogen chloride compared with preparing chlorine from pure raw materials.

[0003] The reaction of electrolysis to obtain chlorine is the most direct, and has been the first choice for industrial recovery of hydrogen chloride to chlorine for a long time [Motupally, S.; Mah, D. T.; Freire, F. J.; Weidner, J. W., Recycling Chlorine from Hydrogen Chloride: A New and Economical Electrolytic Process. The Electrochemical Society Interface 1998, 7, 32.]. However, whether it is electrolysis of hydrogen chloride gas, electrolysis of hydrochloric acid solution, or electrolysis of sodium chloride after neutralization of sodium hydroxide, the energy consumption of the electrolysis process is very large, which makes the cost of electrolysis of hydrogen chloride to chlorine always high.

[0004] In 1774, Carl Scheele used large amounts of manganese dioxide (Mn02) to oxidize hydrogen chloride, obtaining chlorine gas and manganese chloride (MnC12) [Davy, H., Viii. On a Combination of Oxymuriatic Gas and Oxygen Gas. Philosophical Transactions of the Royal Society of London 1811, 101, 155-162.]. Later in 1866, Walter Weldon improved this method, using calcium hydroxide to treat manganese chloride in oxygen, re-oxidizing it, thus achieving the recycling of manganese. This method is still one of the main methods for the preparation of chlorine gas at laboratory scale. But this process consumes a large amount of calcium hydroxide and produces calcium chloride waste, which increases the cost of the reaction and pollutes the environment.

[0005] In 1870, Henry Deacon proposed the use of copper oxide / copper chloride as a catalyst to catalyze the oxidation of hydrogen chloride by oxygen at 426 degrees Celsius (700 Kelvin) to obtain chlorine gas [Deacon H., U.S. Patent 85370, 1868.]. The extremely high temperature not only leads to extremely high energy consumption, but also leads to the instability of the catalyst, rapid deactivation, and the inability to increase the conversion rate. After 150 years, despite the involvement of a large number of scientists in the research and improvement of this technology, no satisfactory solution has been obtained.

[0006] In 2000, Sumitomo Chemical Co., Ltd. of Japan, based on the research of Deacon process, wrapped the ruthenium dioxide film on the surface of rutile titanium dioxide, and realized the oxidation of hydrogen chloride by oxygen at 300 degrees Celsius to prepare chlorine gas [Over, H., Atomic-Scale Understanding of the HC1 Oxidation over Ru02, a Novel Deacon Process. J. Phys. Chem. C 2012, 116, 6779-6792.]. This method has low energy consumption and stable reaction. However, in a long time of reaction, ruthenium dioxide appears to be agglomerated and sintered. Sumitomo Chemical added silicon dioxide to the catalyst to inhibit its agglomeration and sintering. Bayer Company of Germany chose to disperse ruthenium dioxide on the surface of tin oxide and added alumina to inhibit its agglomeration and sintering [Amrute, A. P.; Mondelli, C; Schmidt, T.; Hauert, R.; Perez-Ramirez, J., Industrial Ru02-Based Deacon Catalysts: Carrier Stabilization and Active Phase Content Optimization. ChemCatChem 2013, 5, 748-756.]. The two companies respectively developed Ru02 / Ti02-rutile and Ru02 / Sn02-cassiterite catalysts and put them into production, and established several large-scale hydrogen chloride recovery chlorine production plants in the world. However, the price of noble metal ruthenium is high, which makes the investment cost of this process high. When hydrogen chloride contains hydrogen fluoride impurities, ruthenium dioxide catalyst shows rapid agglomeration and deactivation, which makes the Sumitomo method cannot be directly applied to the fluorine-containing environment. Some scientists try to disperse ruthenium dioxide on the surface of magnesium fluoride as a substitute to resist the agglomeration of ruthenium dioxide in the fluorine-containing environment. Although this technology has developed, it has not been widely used.

[0007] In 1969, Kel-Chlor process developed by W. Kellogg Co. used 80% sulfuric acid as solvent and 1% nitroso sulfuric acid as catalyst, and could produce high-purity chlorine by continuous feeding in multiple reactors and circulating oxidation under heating [Oblad, A. G., The Kel-chlor process. Ind. Eng. Chem. Res. 1969, 61, 23-26.]. However, this reaction has obvious shortcomings. The reaction conditions are extremely acidic, and corrosive substances are produced during the reaction, resulting in very complex equipment, difficult product separation, and high energy consumption, so it is difficult to be widely used.

[0008] A prior art published in 2024 reported a method for chlorinating alkanes by light at room temperature [Xu, L.; Mei, C.; Lu, W., Visible-light-driven oxidative chlorination of alkyl sp 3 C–H bonds with HCl / air at room temperature. Synthesis 2024, 56, 1793-1798.] [Lu Wenjun; Xu Lai; Zhao Mengdi, "A method for preparing chlorinated alkane products." CN114874099, 2022.] However, this method is only used for the chlorination reaction of alkane organic compounds and does not involve the use of sunlight as an energy source for the reaction.

[0009] Patent CN101448737A (Bayer MaterialScience AG, 2009) proposes a method for preparing chlorine from hydrogen chloride and oxygen. Although the method uses a gas permeation method to separate the chlorine and reduce energy consumption, it still requires the use of pure or high-purity oxygen, which is expensive and has poor compatibility with impurities such as fluorine and sulfur.

[0010] Patent CN85109387A (Sankyo Toya Chemical Co., Ltd., 1986) introduces a method for preparing chlorine by oxidizing hydrogen chloride with oxygen-containing gas, but it requires high temperature (300°C-450°C) and special catalysts, high energy consumption and complex operation.

[0011] Currently, most methods for producing chlorine from hydrogen chloride are costly and require high-temperature heating for the reaction to proceed. In addition, metal catalysts have poor compatibility with fluorine, ammonium, and sulfur impurities, and the catalysts are continuously poisoned and deactivated in impure solutions. This has greatly limited the industrial development of chlorine production from hydrogen chloride. Summary of the Invention

[0012] The purpose of the present invention is to provide a method for preparing chlorine in order to overcome the defects of the above-mentioned prior art. The present invention uses a photocatalytic mechanism to efficiently treat impurity-containing hydrogen chloride using nitrogen oxides at normal pressure, without the need for high temperature and precious metal catalysts, significantly reducing costs and improving compatibility. This breaks through the bottleneck of the existing technology and effectively promotes the industrialization of chlorine production from hydrogen chloride.

[0013] The purpose of the present invention can be achieved by the following technical solutions:

[0014] The present invention provides a method for preparing chlorine, comprising the following steps:

[0015] In a light-transmitting reaction vessel, hydrogen chloride, nitrogen oxides, and oxygen-containing gas are mixed and sealed;

[0016] Oxidation reaction occurs under normal pressure and light conditions to generate chlorine gas;

[0017] wherein the light condition is sunlight or simulated light source, the reaction temperature is 0-100℃, and the nitrogen oxide is a catalyst, and in the reaction process, the oxygen is activated by the nitrogen oxide catalyst under the excitation of light energy to form free radicals to realize the oxidation of hydrogen chloride.

[0018] Further, in the light-transmitting reaction vessel, the molar ratio of hydrogen chloride, nitrogen oxide catalyst, and oxygen is 3.96:(0.015-0.15):(0.30-1.00).

[0019] Further, in the reaction process, the nitrogen oxide catalyst generates nitrogen-containing free radicals and active oxygen species under the excitation of light, the active oxygen species reacts with hydrogen chloride to generate chlorine radicals, and the oxygen and hydrogen chloride are continuously consumed through chain transmission.

[0020] Further, in the reaction process, the simulated light source is selected from one of incandescent lamp, straight fluorescent lamp, compact fluorescent lamp, LED lamp, mercury lamp, xenon lamp, and ultraviolet lamp.

[0021] Further, in the reaction process, the simulated light source is LED lamp.

[0022] Further, the nitrogen oxide is selected from one of nitric acid, nitrous acid, nitrate, nitrite, and nitrogen oxide.

[0023] Further, the nitrogen oxide is sodium nitrite or sodium nitrate.

[0024] Further, the hydrogen chloride is in any of the following forms

[0025] Gaseous hydrogen chloride;

[0026] Hydrochloric acid solution with a concentration of 35wt%-40wt%.

[0027] Further, the oxygen-containing gas is selected from any of the following:

[0028] Air atmosphere with an oxygen partial pressure of 0.21atm;

[0029] Pure oxygen atmosphere with an oxygen partial pressure of 1.0atm;

[0030] Oxygen dilution gas with an oxygen partial pressure of ≥0.01atm.

[0031] Further, the reaction is carried out in the presence of water or organic solvent;

[0032] When the solvent is water, the addition amount is 0.05-0.5% of the total volume of the reaction system, preferably 0.1%;

[0033] When the solvent is an organic solvent, the addition amount is 0.1-1% of the total volume of the reaction system, preferably 0.1-0.6%.

[0034] Further preferably, the organic solvent is nitromethane or trifluoroacetic acid.

[0035] In terms of specific mechanism, the present application utilizes nitrogen oxides (such as nitrite and nitrate) as catalysts, which are activated under light conditions. The photocatalytic mechanism is different from the traditional mechanism that relies on high temperature or metal catalysts, and does not depend on active sites that are easily poisoned by impurities. Nitrogen oxides produce active radicals under photoexcitation, directly initiating oxidation reactions, and significantly reducing the sensitivity to impurities. The activity of the catalyst is not affected by the chemical adsorption or poisoning of impurities such as fluorine and sulfur, avoiding the rapid deactivation problem of traditional metal catalysts (such as ruthenium-based catalysts) caused by impurity adsorption.

[0036] In terms of specific mechanism, the present application is carried out at room temperature and pressure, avoiding the risk of side reactions between impurities and catalysts under high temperature and pressure conditions. For example, at high temperatures, fluoride impurities are easily reacted with metal catalysts to form stable fluorides, resulting in catalyst failure; while at room temperature, the risk is significantly reduced. The reaction proceeds through free radicals, which have high chemical activity and non-selectivity, enabling simultaneous treatment of hydrogen chloride and impurities. Even with a small amount of fluorine, sulfur and other impurities, free radicals can still efficiently transfer energy and electrons, maintaining the progress of the reaction. The non-selective mechanism makes the reaction system naturally fault-tolerant to impurities.

[0037] Compared with the prior art, the present application has the following beneficial effects:

[0038] 1) The reaction method of the present application has significant energy-saving advantages, as the energy source is sunlight or simulated light source, completely avoiding the high-temperature heating process required by traditional chlorine production methods, thereby greatly reducing energy consumption and achieving efficient use of energy.

[0039] 2) The method of the present application can operate efficiently at room temperature and pressure, without the need for extreme temperature or pressure, which not only reduces the need for complex and expensive equipment, but also significantly improves the safety and convenience of operation, making the production of chlorine more simple and easy.

[0040] 3) Compared with traditional processes, the synthesis path of the present application is shorter, without the need for pre-neutralization of hydrogen chloride and electrolysis, thereby saving a large amount of chemical raw materials and energy consumption, reducing production costs, and reducing waste generation, which is more economical and environmentally friendly.

[0041] 4) In terms of raw material selection, the present application uses simple and low-cost air as the oxidant, which greatly reduces the cost of raw materials compared to methods using pure oxygen or other special oxidants, improving the economic efficiency of the process.

[0042] 5) The catalyst used in the present application is common nitrite and nitrate, which is more affordable and easier to obtain than traditional noble metal catalysts, thus helping to reduce production costs and improve the popularity of the process.

[0043] 6) The reaction system has strong adaptability to raw materials, and strict dehydration and deoxidation pretreatment of the raw materials is not required. Even if the raw material contains impurities such as fluorine and sulfur, the catalyst will not be disabled, which enables the present application to directly use industrial by-product hydrogen chloride containing impurities, broadens the source of raw materials, and enhances the feasibility of industrial application.

[0044] 7) The reaction process of the present application is clean and environmentally friendly, and the only by-product is water, without other harmful substances, which does not pollute the environment and meets the requirements of sustainable development, thus helping to reduce the impact of chemical production on the environment. DETAILED DESCRIPTION

[0045] Overall, the present application innovatively uses sunlight or simulated light source as energy to generate chlorine gas by catalytic oxidation of hydrogen chloride gas or hydrochloric acid solution using nitrogen oxides at room temperature. The method of the present application does not require high temperature heating, significantly reduces energy consumption, and is simple and safe to operate. Through the photocatalysis of nitrogen oxides, the reaction can be efficiently carried out at room temperature and normal pressure, avoiding the complex pretreatment and electrolysis steps in traditional methods, and saving a large amount of chemical raw materials and energy. Using air as the oxidant and simple nitrite and nitrate as the catalyst, the cost is reduced and the economic efficiency of the process is improved. The present application has strong compatibility to raw materials and can handle hydrogen chloride containing fluorine, sulfur and other impurities, which broadens the source of raw materials and enhances the feasibility of industrial application. The only by-product is water, which is environmentally friendly and meets the requirements of sustainable development. The method provides an energy-saving, environmentally friendly and efficient solution for the industrial production of chlorine.

[0046] The present application will be described in detail below with reference to specific embodiments. If the preparation means, materials, structures or composition ratios and other features in the present technical solution are not explicitly described, they are regarded as common technical features disclosed in the prior art.

[0047] The following examples will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be pointed out that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made. These all belong to the protection scope of the present application.

[0048] Example 1

[0049]

[0050] Under air at room temperature, sodium nitrite (10 mg, 0.15 mmol) was added to the flask followed by hydrogen chloride gas (97 mL, 3.96 mmol). After the flask was sealed, it was illuminated with a 10-watt LED lamp at a distance of 1 cm from the flask for 1 hour. Upon completion of the reaction, a yellow-green gas was obtained. Cyclohexane was added to the reaction for testing, and the yield of chlorine gas was calculated to be 100%.

[0051] This example illustrates a reaction in which the energy source is sunlight, the reaction temperature is room temperature, the reactants are hydrogen chloride gas and air, the catalyst is a nitrite salt, and no solvent is added.

[0052] Example 2

[0053]

[0054] Under air at room temperature, sodium nitrite (10 mg, 0.15 mmol) was added to the flask followed by hydrogen chloride gas (97 mL, 3.96 mmol). After the flask was sealed, it was illuminated with a 10-watt LED lamp at a distance of 1 cm from the flask for 1 hour. Upon completion of the reaction, a yellow-green gas was obtained. Cyclohexane was added to the reaction for testing, and the yield of chlorine gas was calculated to be 100%.

[0055] This example illustrates a reaction in which the energy source is a simulated light source.

[0056] Example 3

[0057]

[0058] Under air at room temperature, sodium nitrite (10 mg, 0.15 mmol) was added to the flask followed by hydrogen chloride gas (97 mL, 3.96 mmol). After the flask was sealed, it was illuminated with a 10-watt LED lamp at a distance of 1 cm from the flask for 0.5 hour. Upon completion of the reaction, a yellow-green gas was obtained. Cyclohexane was added to the reaction for testing, and the yield of chlorine gas was calculated to be 51.7%.

[0059] This example illustrates a reaction in which the energy source is a simulated light source.

[0060] Example 4

[0061]

[0062] Under air at room temperature, sodium nitrite (10 mg, 0.15 mmol) was added to the flask followed by hydrogen chloride gas (97 mL, 3.96 mmol). After the flask was sealed, it was illuminated with a 10-watt LED lamp at a distance of 1 cm from the flask for 1 hour. Upon completion of the reaction, a yellow-green gas was obtained. Cyclohexane was added to the reaction for testing, and the yield of chlorine gas was calculated to be 10.0%.

[0063] This example illustrates a reaction in which the energy source is a simulated light source.

[0064] Example 5

[0065]

[0066] Under air at room temperature, sodium nitrite (10 mg, 0.15 mmol) was added to the sealed tube followed by hydrogen chloride gas (97 mL, 3.96 mmol). After sealing the tube, a 10 watt LED lamp was placed 1 cm from the tube and the reaction was heated to 70 °C with a hot air gun. The reaction was irradiated for 1 hour. Upon completion of the reaction, a yellow-green gas was produced. Cyclohexane was added to the reaction and the yield of chlorine gas was calculated to be 100%.

[0067] This example illustrates a reaction with an energy source of simulated light and a temperature of 70 °C.

[0068] Example 6

[0069]

[0070] Under air at room temperature, sodium nitrite (10 mg, 0.15 mmol) was added to the sealed tube followed by hydrogen chloride gas (97 mL, 3.96 mmol). After sealing the tube, a 10 watt LED lamp was placed 1 cm from the tube and the reaction was heated to 0 °C with an ice water bath. The reaction was irradiated for 6 hours. Upon completion of the reaction, a yellow-green gas was produced. Cyclohexane was added to the reaction and the yield of chlorine gas was calculated to be 100%.

[0071] This example illustrates a reaction with an energy source of simulated light and a temperature of 0 °C.

[0072] Example 7

[0073]

[0074] Under air at room temperature, sodium nitrite (10 mg, 0.15 mmol) was added to the sealed tube followed by hydrogen chloride gas (97 mL, 3.96 mmol). After sealing the tube, a 10 watt LED lamp was placed 1 cm from the tube and the reaction was heated to 100 °C with a water bath. The reaction was irradiated for 6 hours. Upon completion of the reaction, a yellow-green gas was produced. Cyclohexane was added to the reaction and the yield of chlorine gas was calculated to be 100%.

[0075] This example illustrates a reaction with an energy source of simulated light and a temperature of 100 °C.

[0076] Example 8

[0077]

[0078] Under air at room temperature, sodium nitrite (1 mg, 0.015 mmol) was added to the sealed tube followed by hydrogen chloride gas (97 mL, 3.96 mmol). After sealing the tube, a 10 watt LED lamp was placed 1 cm from the tube and the reaction was irradiated for 12 hours. Upon completion of the reaction, a yellow-green gas was produced. Cyclohexane was added to the reaction and the yield of chlorine gas was calculated to be 89.4%.

[0079] This example illustrates a reaction with an energy source of simulated light and a starting material of a solution of hydrogen chloride.

[0080] Example 9

[0081]

[0082] Under air at room temperature, sodium nitrite (1 mg, 0.015 mmol), potassium fluoride (9 mg, 0.15 mmol), hydrochloric acid (37%, 3.3 mL, 3.96 mmol) were added sequentially in a sealed tube. A 10 watt LED lamp was placed 1 cm from the tube and irradiated for 12 hours. A yellow-green gas was produced upon completion of the reaction. Cyclohexane was added to the reaction for testing and the yield of chlorine gas was calculated to be 85.1%.

[0083] This example illustrates a reaction in which the energy source is simulated light and the starting material is a mixture of hydrochloric acid containing an impurity (fluoride).

[0084] Example 10

[0085]

[0086] Under air at room temperature, sodium nitrite (1 mg, 0.015 mmol), ammonium chloride (8 mg, 0.15 mmol), hydrochloric acid (37%, 3.3 mL, 3.96 mmol) were added sequentially in a sealed tube. A 10 watt LED lamp was placed 1 cm from the tube and irradiated for 12 hours. A yellow-green gas was produced upon completion of the reaction. Cyclohexane was added to the reaction for testing and the yield of chlorine gas was calculated to be 86.4%.

[0087] This example illustrates a reaction in which the energy source is simulated light and the starting material is a mixture of hydrochloric acid containing an impurity (ammonium).

[0088] Example 11

[0089]

[0090] Under air at room temperature, sodium nitrite (1 mg, 0.015 mmol), sodium sulfide (1 mg, 0.015 mmol), hydrochloric acid (37%, 3.3 mL, 3.96 mmol) were added sequentially in a sealed tube. A 10 watt LED lamp was placed 1 cm from the tube and irradiated for 12 hours. A yellow-green gas was produced upon completion of the reaction. Cyclohexane was added to the reaction for testing and the yield of chlorine gas was calculated to be 87.1%.

[0091] This example illustrates a reaction in which the energy source is simulated light and the starting material is a mixture of hydrochloric acid containing an impurity (sulfide).

[0092] Example 12

[0093]

[0094] Under air at room temperature, a tube was charged with sodium nitrite (10 mg, 0.15 mmol), hydrogen chloride gas (97 mL, 3.96 mmol), and pure oxygen (17 mL, 0.70 mmol). The tube was capped and a 10 watt LED lamp was placed 1 cm from the tube. The reaction was illuminated for 3 hours. At the end of the reaction, a yellow-green gas was produced. Cyclohexane was added to the reaction and the yield of chlorine gas was calculated to be 50.0%.

[0095] This example illustrates a reaction in which the energy source is simulated light and the oxygen is pressurized diluent gas.

[0096] Example 13

[0097]

[0098] Under air at room temperature, a tube was charged with sodium nitrite (10 mg, 0.15 mmol), hydrogen chloride gas (97 mL, 3.96 mmol), and pure oxygen (17 mL, 0.70 mmol). The tube was capped and a 10 watt LED lamp was placed 1 cm from the tube. The reaction was illuminated for 3 hours. At the end of the reaction, a yellow-green gas was produced. Cyclohexane was added to the reaction and the yield of chlorine gas was calculated to be 50.0%.

[0099] This example illustrates a reaction in which the energy source is simulated light and the oxygen is pressurized diluent gas.

[0100] Example 14

[0101]

[0102] Under air at room temperature, a tube was charged with sodium nitrite (10 mg, 0.15 mmol), hydrogen chloride gas (97 mL, 3.96 mmol), and pure oxygen (17 mL, 0.70 mmol). The tube was capped and a 10 watt LED lamp was placed 1 cm from the tube. The reaction was illuminated for 3 hours. At the end of the reaction, a yellow-green gas was produced. Cyclohexane was added to the reaction and the yield of chlorine gas was calculated to be 50.0%.

[0103] This example illustrates a reaction in which the energy source is simulated light and the oxygen is pressurized diluent gas.

[0104] Example 15

[0105]

[0106] Under air at room temperature, a tube was charged with sodium nitrite (10 mg, 0.15 mmol), hydrogen chloride gas (97 mL, 3.96 mmol), and pure oxygen (17 mL, 0.70 mmol). The tube was capped and a 10 watt LED lamp was placed 1 cm from the tube. The reaction was illuminated for 3 hours. At the end of the reaction, a yellow-green gas was produced. Cyclohexane was added to the reaction and the yield of chlorine gas was calculated to be 50.0%.

[0107] This example illustrates a reaction in which the energy source is simulated light and the oxygen is pressurized diluent gas.

[0108] Example 16

[0109]

[0110] Under room temperature air, sodium nitrite (10 mg, 0.15 mmol), nitromethane (0.1 mL), hydrogen chloride gas (97 mL, 3.96 mmol) were added into the sealed tube sequentially. After sealing the tube, a 10-watt LED lamp was placed 1 cm away from the tube and irradiated for 1 hour. Yellow-green gas was obtained at the end of the reaction. Cyclohexane was added for reaction detection, and the yield of chlorine gas was calculated to be 100%.

[0111] This example illustrates a reaction in which the energy source is simulated light and the solvent added is an organic solvent.

[0112] Example 17

[0113]

[0114] Under room temperature air, sodium nitrite (10 mg, 0.15 mmol), nitromethane (0.1 mL), hydrogen chloride gas (97 mL, 3.96 mmol) were added into the sealed tube sequentially. After sealing the tube, a 10-watt LED lamp was placed 1 cm away from the tube and irradiated for 1 hour. Yellow-green gas was obtained at the end of the reaction. Cyclohexane was added for reaction detection, and the yield of chlorine gas was calculated to be 100%.

[0115] This example illustrates a reaction in which the energy source is simulated light and the solvent added is an organic solvent.

[0116] Comparative Example 1

[0117]

[0118] Under room temperature air, sodium nitrite (10 mg, 0.15 mmol), hydrogen chloride gas (97 mL, 3.96 mmol) were added into the sealed tube sequentially. After sealing the tube, the tube was wrapped in black cloth to avoid light, and the reaction was carried out for 24 hours. No yellow-green gas was observed at the end of the reaction. Cyclohexane was added for reaction detection, and no chlorine gas was detected, with a chlorine gas yield of 0%.

[0119] This comparative example illustrates a reaction without light, proving that the reaction cannot be started without light and the necessity of a light-transmitting material.

[0120] Comparative Example 2

[0121]

[0122] At room temperature and in air, sodium nitrite (10 mg, 0.15 mmol) and hydrogen chloride gas (97 mL, 3.96 mmol) were added sequentially to a sealed tube. The tube was then covered with black cloth to protect from light and heated with hot air at 70°C for 24 hours. No yellow-green gas was observed upon completion of the reaction. Cyclohexane was added for detection, but no chlorine was detected, resulting in a 0% chlorine yield.

[0123] This comparative example illustrates the reaction without light and at a temperature of 70 degrees Celsius, proving that heating cannot supplement light.

[0124] Comparative Example 3

[0125]

[0126] Sodium chloride (9 mg, 0.15 mmol) and hydrogen chloride gas (97 mL, 3.96 mmol) were added sequentially to a sealed tube under air at room temperature. A 10-watt LED light was placed 1 cm from the tube and illuminated for 24 hours. No yellow-green gas was observed upon completion of the reaction. Cyclohexane was added for reaction analysis, but no chlorine was detected, resulting in a 0% chlorine yield.

[0127] This comparative example illustrates the reaction without nitrogen oxides, proving the necessity of nitrogen oxides.

[0128] Comparative Example 4

[0129]

[0130] Sodium nitrite (10 mg, 0.15 mmol) was added to the sealed tube under air at room temperature. After sealing, a 10-watt LED light was placed 1 cm from the tube and illuminated for 24 hours. No yellow-green gas was observed upon completion of the reaction. Cyclohexane was added to the reaction, but no chlorine was detected, resulting in a 0% chlorine yield.

[0131] This comparative example illustrates the reaction without nitrogen oxides, demonstrating the necessity of hydrogen chloride.

[0132] Comparative Example 5

[0133]

[0134] At room temperature and in air, sodium nitrite (1 mg, 0.015 mmol) and hydrogen chloride gas (97 mL, 3.96 mmol) were added sequentially to a sealed tube. The atmosphere was then evacuated and replaced with nitrogen. After sealing, a 10-watt LED light was placed 1 cm from the tube and illuminated for 24 hours. A small amount of yellow-green gas was released upon completion of the reaction. Cyclohexane was added for detection, and 0.007 mmol of chlorine was detected, indicating a chlorine yield that did not exceed the catalyst input.

[0135] This comparative example illustrates the reaction in the absence of oxygen, demonstrating the necessity of oxygen.

[0136] In summary, the embodiments of the present application demonstrate an innovative method for producing chlorine gas. This method drives the reaction of hydrogen chloride and oxygen to generate chlorine gas at room temperature and normal pressure, with the help of sunlight or simulated light source energy, using nitrogen oxides as catalyst. Mechanistically, the nitrogen oxide catalyst is activated under light conditions, initiating a free radical reaction, thereby achieving efficient oxidation of hydrogen chloride. This process does not require external heating, significantly reducing energy consumption, and can operate stably in raw material systems containing impurities, overcoming the high purity requirements of traditional methods.

[0137] In terms of technical effects, the method of the present application exhibits excellent performance. Multiple experiments in the embodiments have proven that, whether under standard lighting conditions or under different temperatures, different light source intensities, and different raw material compositions, chlorine gas can be effectively generated. This indicates that the method has wide adaptability to operating conditions and can flexibly meet different production demands. In addition, the use of common nitrogen oxides as catalyst not only has low cost, but also is easy to obtain, greatly reducing production costs and improving economic benefits compared to traditional noble metal catalysts.

[0138] Further analysis of the embodiments can find that the method of the present application has strong compatibility to raw materials. Whether hydrogen chloride exists in the form of gas or in the form of impurity-containing hydrochloric acid solution, the reaction can be successfully carried out to generate the target product. This means that the method can directly use the by-product hydrogen chloride produced in industrial production without complex pretreatment steps, thereby simplifying the process flow, reducing resource waste, and enhancing the feasibility and environmental friendliness of industrial application.

[0139] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. Those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative labor. Therefore, the present application is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present application without departing from the scope of the present application should be within the scope of protection of the present application.

Claims

1. A method for preparing chlorine, characterized in that: The following steps are involved: In a light-transmitting reaction vessel, hydrogen chloride, nitrogen oxides, and oxygen-containing gas are mixed and sealed; Oxidation reaction occurs under normal pressure and light conditions to generate chlorine gas; The illumination condition is sunlight or simulated light source, the reaction temperature is 0-100° C., the nitrogen oxide is a catalyst, and during the reaction, light energy excites the nitrogen oxide catalyst to activate oxygen, forming a free radical reaction to achieve oxidation of hydrogen chloride.

2. The method for preparing chlorine according to claim 1, wherein: In a light-transmitting reaction container, the molar ratio of hydrogen chloride, nitrogen oxide catalyst, and oxygen is 3.96: (0.015-0.15): (0.30-1.00).

3. The method for preparing chlorine according to claim 1, wherein: During the reaction, the nitrogen oxide catalyst generates nitrogen-containing free radicals and active oxygen species under light excitation. The active oxygen species react with hydrogen chloride to generate chlorine free radicals, and continuously consume oxygen and hydrogen chloride through free radical reactions.

4. The method for preparing chlorine according to claim 1, wherein: During the reaction process, the simulated light source is selected from one of an incandescent lamp, a straight fluorescent lamp, a compact fluorescent lamp, an LED lamp, a mercury lamp, a xenon lamp, and an ultraviolet lamp.

5. The method for preparing chlorine according to claim 4, wherein: During the reaction process, the simulated light source is an LED lamp.

6. The method for preparing chlorine according to claim 1, wherein: The nitrogen oxide is selected from one of nitric acid, nitrous acid, nitrate, nitrite and nitrogen oxide.

7. The method for preparing chlorine according to claim 6, wherein: The nitrogen oxide is sodium nitrite or sodium nitrate.

8. The method for preparing chlorine according to claim 1, wherein: The hydrogen chloride is in any of the following forms Gaseous hydrogen chloride; A hydrochloric acid solution with a concentration of 35wt%-40wt%.

9. The method for preparing chlorine according to claim 1, wherein: The oxygen-containing gas is selected from any one of the following: Air atmosphere, oxygen partial pressure 0.21 atm; Pure oxygen atmosphere, oxygen partial pressure 1.0 atm; Oxygen diluent, oxygen partial pressure ≥ 0.01atm.

10. The method for preparing chlorine according to claim 1, wherein: The reaction is carried out in the presence of water or an organic solvent; When the solvent is water, the added amount accounts for 0.05-0.5% of the total volume of the reaction system; When the solvent is an organic solvent, the added amount accounts for 0.1 to 1% of the total volume of the reaction system.

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