A method for low temperature production of sulfur tetrafluoride

Abstract

The application provides a method for preparing sulfur tetrafluoride at low temperature, which comprises the following steps: reacting iodine pentafluoride with sulfur dissolved in carbon disulfide under the temperature condition of 0-50 DEG C to prepare sulfur tetrafluoride. The application can efficiently react at low temperature by adopting the reaction of iodine pentafluoride and carbon disulfide dissolved sulfur, avoids the problems of high energy consumption and difficult control of the reaction of molten sulfur, greatly improves the production safety, and the method of the application does not produce fluorocarbon compounds to destroy ozone, the selected solvent does not participate in the reaction, greatly reduces the generation of harmful substances, saves raw materials, and saves industrialization cost. In addition, the product purification process of the application is simple, the by-products are clear and easy to recover, the by-products and the solvent can be recycled, resource recycling is realized, waste and pollution are avoided.

Description

Technical Field

[0001] This invention relates to the field of fluorochemical technology, and in particular to a method for preparing sulfur tetrafluoride at low temperature. Background Technology

[0002] Sulfur tetrafluoride (SF4) is currently the most widely used and effective selective organic fluorinating agent. It can selectively fluorinate carbonyl and hydroxyl groups (replacing oxygen in carbonyl-containing compounds). It is widely used in the fine chemical industry for the production of high-end liquid crystal materials and intermediates in high-end pharmaceutical and pesticide industries, and has an irreplaceable position.

[0003] The selective fluorination properties of sulfur tetrafluoride are manifested in applications such as the conversion of 5-nitrofuranic acid to 2-trifluoromethyl-5-nitrofuran; the fluorination of 5-carboxylic acid uracil to 5-trifluoromethyluracil with a yield of 77%; and the conversion of aryl fluorocarbonates or phenolic perfluoroalkyl esters into aryl perfluoroalkyl ethers, among others. These substances play an important role in pharmaceuticals and surfactants. High-purity sulfur tetrafluoride can also be used in electronic gases, gas etchants, and chemical vapor deposition.

[0004] Currently, the main methods for preparing sulfur tetrafluoride include fluorination with fluorine gas, fluorination with hydrofluoric acid, fluorination with organic base hydrofluoric acid salts, and fluorination with metal fluoride salts. Looking at the current methods for synthesizing sulfur tetrafluoride both domestically and internationally, the sulfur used is mostly fed in a molten state, or directly fluorinated with fluorine gas, or the reaction is carried out at high temperatures. These methods involve vigorous and difficult-to-control reactions, high energy consumption, and significant toxicity. Alternatively, they use highly hazardous chlorinated sulfur compounds as solvents, which have low boiling points, are unstable, and decompose easily, making the reaction difficult to control and easily producing ozone-depleting fluorides, causing significant environmental impact. Summary of the Invention

[0005] This invention provides a method for preparing sulfur tetrafluoride at low temperature, which solves the defects of poor safety, high energy consumption and environmental impact in the prior art, and achieves high yield, low energy consumption, safety and reliability, and is more environmentally friendly.

[0006] The present invention provides a method for preparing sulfur tetrafluoride, comprising: reacting iodine pentafluoride with sulfur dissolved in carbon disulfide at a temperature of 0-50°C to prepare sulfur tetrafluoride.

[0007] This invention breaks with the conventional method of using molten sulfur in the reaction. Instead, it dissolves sulfur in carbon disulfide and reacts it with iodine pentafluoride. This reaction can be carried out at low temperatures of 0-50°C, and even at room temperature, it can proceed as a relatively fast liquid-liquid reaction. The reaction is characterized by low temperature, low energy consumption, high safety, and high yield. It also avoids the violent reactions that occur at higher temperatures, preventing further oxidation to sulfur hexafluoride at high temperatures and ensuring the stability of sulfur tetrafluoride.

[0008] The reaction formula is as follows:

[0009]

[0010] Furthermore, the produced sulfur tetrafluoride is in a gaseous state, while other components such as solvents and impurities are in other states, making them extremely easy to separate. Based on Gibbs free energy calculations and experimental verification, no fluorocarbons are produced as byproducts, thus avoiding ozone layer depletion; moreover, both the solvent and impurities can be recycled, and the purification process is simple and easy to operate.

[0011] According to the method for preparing sulfur tetrafluoride provided by the present invention, the sulfur is preferably a raw material with low moisture content and high sulfur content.

[0012] In some embodiments of the present invention, the sulfur has a sulfur content ≥95% and a moisture content less than 100 ppm; the carbon disulfide has a purity ≥99%. Controlling the moisture content is beneficial for subsequent processing and improving yield.

[0013] According to the method for preparing sulfur tetrafluoride provided by the present invention, the mass ratio of sulfur to carbon disulfide is 1:1.5-3.

[0014] The present invention has found that the mass ratio of carbon disulfide to sulfur has a certain impact on the reaction results, and the effect is better when it is controlled within the above range.

[0015] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0016] In embodiments of the present invention, the mass ratio of sulfur to carbon disulfide can be any ratio between 1:1.5 and 3, for example, 1:1.5, 1:1.8, 1:2, 1:2.3, 1:2.5, 1:2.7, 1:2.8, 1:3, 1:3.2, and 1:3.5.

[0017] According to the method for preparing sulfur tetrafluoride provided by the present invention, the iodine pentafluoride has a purity of ≥99.5% and is obtained by distillation purification, preferably at a distillation temperature of 100-104.5℃.

[0018] According to the method for preparing sulfur tetrafluoride provided by the present invention, the mass ratio of iodine pentafluoride to sulfur is 4:5.2-6.0.

[0019] In some existing preparation methods, it is emphasized that iodine pentafluoride should be used in appropriate excess. However, this invention has found that controlling the mass ratio of iodine pentafluoride to sulfur within the above range will not significantly affect the reaction process. On the contrary, it is beneficial to save costs because the unit price of iodine pentafluoride is extremely high.

[0020] According to the method for preparing sulfur tetrafluoride provided by the present invention, the reaction temperature is preferably 15-30°C. At this temperature, the reaction can proceed smoothly without the need for additional heating or cooling equipment, thus saving energy.

[0021] According to the method for preparing sulfur tetrafluoride provided by the present invention, stirring is carried out during the reaction process at a stirring speed of 10-30 r / min.

[0022] Stirring during the reaction is beneficial for the uniform mixing of materials, but the stirring speed should not be too fast, otherwise the reaction will be violent and difficult to control, causing safety risks; moreover, the generation of gas too quickly will lead to excessive by-products, causing blockage of equipment and pipelines.

[0023] According to the method for preparing sulfur tetrafluoride provided by the present invention, after the reaction is completed, the crude gas obtained is collected after preliminary condensation to remove impurities; preferably, the condensation temperature is 0-10℃.

[0024] After the above preliminary condensation and impurity removal process, byproducts such as elemental iodine and solvent carbon disulfide can be removed, and the resulting sulfur tetrafluoride product has a purity of approximately 95%.

[0025] According to the method for preparing sulfur tetrafluoride provided by the present invention, an inert gas protection is provided throughout the reaction process.

[0026] Because moisture in the air can affect the reaction, an inert gas is used for protection throughout the entire reaction process. For example, the reactor is purged with inert gas before the reactants are added.

[0027] In this invention, the inert gas refers to gases such as helium, argon, and nitrogen that do not participate in the process reaction, with nitrogen being the preferred protective gas.

[0028] In some embodiments of the present invention, the method for preparing sulfur tetrafluoride includes the following steps:

[0029] S1. Add sulfur to a stainless steel stirred tank, pump in carbon disulfide solution and stir to dissolve, separate the liquid to remove water, take the lower layer solution, filter and pump it into a solvent tank for later use.

[0030] Iodine pentafluoride was purified by distillation and then stored in a steel cylinder for later use.

[0031] S2. Add carbon disulfide containing sulfur dissolved in S1 to the stainless steel reactor after nitrogen purging, and keep the reactor at a constant temperature by circulating cold water.

[0032] S3. Slowly and continuously add purified iodine pentafluoride to the reactor and stir the reaction.

[0033] S4. The crude gas obtained from the reaction is collected after preliminary condensation to remove impurities.

[0034] Furthermore, in step S1, the stainless steel stirring tank is equipped with a circulating water cooling system, a stirring device, an insoluble matter filtration device, an explosion-proof solvent pump, and other functions.

[0035] More preferably, the cooling water temperature of the stainless steel stirring vessel is maintained at 15-30°C, the stirring speed is controlled at 20-50 r / min, and nitrogen is used for purging before dissolution to remove all air from the vessel.

[0036] Furthermore, in step S2, the circulating water temperature is maintained at 15-30℃, which is the same as the reaction temperature in step S3. In step S3, the stirring speed is 10-30 r / min.

[0037] Further, in step S1, the mass ratio of sulfur to carbon disulfide is 1:1.5-3; in step S3, the mass ratio of iodine pentafluoride to sulfur is 4:5.2-6.0.

[0038] This invention provides a method for preparing sulfur tetrafluoride at low temperatures. By using iodine pentafluoride to react with dissolved sulfur in carbon disulfide, the reaction can be carried out efficiently at low temperatures, avoiding the problems of high energy consumption and difficulty in controlling the reaction caused by direct reaction of molten sulfur, thus greatly improving production safety. Moreover, the method of this invention does not produce fluorocarbons that destroy ozone, and the selected solvent does not participate in the reaction, greatly reducing the generation of harmful substances, saving raw materials, and reducing industrialization costs.

[0039] Furthermore, the crude product obtained by the method of the present invention can achieve a purity of over 91%, the product purification process is simple, and the purity can reach over 99.0% after subsequent purification; the by-products are clearly identified and easy to recover, and both the by-products and the solvent can be recycled, with a maximum recovery rate of up to 97%, realizing resource recycling and reuse, and avoiding waste and pollution. Attached Figure Description

[0040] Figure 1 This is a process flow diagram for preparing sulfur tetrafluoride in an embodiment of the present invention. Detailed Implementation

[0041] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "specific implementation," or "some specific implementations," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0043] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0044] In the following examples, unless otherwise specified, all "%" refers to mass percentage.

[0045] Example 1

[0046] This embodiment provides a method for preparing sulfur tetrafluoride at low temperature, and the process flow diagram is shown below. Figure 1 As shown, the specific steps are as follows:

[0047] (1) Preparation of sulfur-containing solution: Weigh 58.5 kg of industrial sulfur (99%) and dissolve it in 146 kg of carbon disulfide. After dissolving, let it stand to separate into layers, remove the lower layer, filter to remove the insoluble matter in the upper layer, and obtain a mixed solution for later use.

[0048] (2) Purification of iodine pentafluoride: Iodine pentafluoride was distilled at 100.5℃, and 300 kg of the middle fraction with a content ≥99.5% was collected and bottled for later use;

[0049] (3) Continuous reaction: Add the mixture in (1) to a stainless steel reactor that has been purged with nitrogen and tested to be qualified (<80ppm). Maintain the reactor temperature at 25-30℃ and continuously introduce the iodine pentafluoride in (2) under micro-stirring (stirring speed 10-30r / min) to carry out the reaction. The rate of introducing iodine pentafluoride is adjusted by the change in the rate of sulfur tetrafluoride formation. After the iodine pentafluoride is consumed, continue stirring the reaction for 30min and then stop the reaction.

[0050] (4) Crude product gas detection: Sulfur tetrafluoride was continuously collected during the reaction. After preliminary cooling (temperature 0-10℃), 173 kg of gaseous crude sulfur tetrafluoride was obtained. After external testing, the sulfur tetrafluoride content (purity) was 93.8%, and the yield was calculated to be 88.86% based on the raw materials.

[0051] Example 2

[0052] This embodiment provides a method for preparing sulfur tetrafluoride at low temperature, the specific steps of which are as follows:

[0053] (1) Preparation of sulfur-containing solution: Weigh 58.5 kg of industrial sulfur (99%) and dissolve it in 134.6 kg of carbon disulfide. After dissolving, let it stand to separate into layers, remove the lower layer, filter to remove the insoluble matter in the upper layer, and obtain a mixed solution for later use.

[0054] (2) Purification of iodine pentafluoride: Iodine pentafluoride was distilled at 100.5℃, and 300 kg of the middle fraction with a content ≥99.5% was collected and bottled for later use;

[0055] (3) Continuous reaction: Add the mixture in (1) to a stainless steel reactor that has been purged with nitrogen and tested to be qualified (<80ppm). Maintain the reactor temperature at 25-30℃ and continuously introduce the iodine pentafluoride in (2) under micro-stirring (stirring speed 10-30r / min) to carry out the reaction. The rate of introducing iodine pentafluoride is adjusted by the change in the rate of sulfur tetrafluoride formation. After the iodine pentafluoride is consumed, continue stirring the reaction for 30min and then stop the reaction.

[0056] (4) Crude product gas detection: The reaction process temperature fluctuates between 23 and 29°C. Sulfur tetrafluoride is collected and after preliminary condensation (temperature 0 to 10°C), 176.8 kg of crude sulfur tetrafluoride is obtained. After external testing, the sulfur tetrafluoride content is 95.1%, and the yield is 92.1% based on the raw materials.

[0057] Example 3

[0058] This embodiment provides a method for preparing sulfur tetrafluoride at low temperature, the specific steps of which are as follows:

[0059] (1) Preparation of sulfur-containing solution: Weigh 58.5 kg of industrial sulfur (99%) and dissolve it in 163.8 kg of carbon disulfide. After dissolving, let it stand to separate into layers, remove the lower layer, filter to remove the insoluble matter in the upper layer, and obtain a mixed solution for later use.

[0060] (2) Purification of iodine pentafluoride: Iodine pentafluoride was distilled at 100.5℃, and 300 kg of the middle fraction with a content ≥99.5% was collected and bottled for later use;

[0061] (3) Continuous reaction: Add the mixture in (1) to a stainless steel reactor that has been purged with nitrogen and tested to be qualified (<80ppm). Maintain the reactor temperature at 25-30℃ and continuously introduce the iodine pentafluoride in (2) under micro-stirring (stirring speed 10-30r / min) to carry out the reaction. The rate of introducing iodine pentafluoride is adjusted by the change in the rate of sulfur tetrafluoride formation. After the iodine pentafluoride is consumed, continue stirring the reaction for 30min and then stop the reaction.

[0062] (4) Crude product gas detection: The reaction process temperature fluctuates between 23 and 29°C. Sulfur tetrafluoride is collected and after preliminary condensation (temperature 0 to 10°C), 173.4 kg of crude sulfur tetrafluoride is obtained. After external testing, the sulfur tetrafluoride content is 92.6%, and the yield is calculated to be 87.9% based on the raw materials.

[0063] Example 4

[0064] This embodiment provides a method for preparing sulfur tetrafluoride at low temperature, the specific steps of which are as follows:

[0065] (1) Preparation of sulfur-containing solution: Weigh 59.6 kg of industrial sulfur (99%) and dissolve it in 137.1 kg of carbon disulfide. After dissolving, let it stand to separate into layers, remove the lower layer, filter to remove the insoluble matter in the upper layer, and obtain a mixed solution for later use.

[0066] (2) Purification of iodine pentafluoride: Iodine pentafluoride was distilled at 100.5℃, and 300 kg of the middle fraction with a content ≥99.5% was collected and bottled for later use;

[0067] (3) Continuous reaction: Add the mixture in (1) to a stainless steel reactor that has been purged with nitrogen and tested to be qualified (<80ppm). Maintain the reactor temperature at 25-30℃ and continuously introduce the iodine pentafluoride in (2) under micro-stirring (stirring speed 10-30r / min) to carry out the reaction. The rate of introducing iodine pentafluoride is adjusted by the change in the rate of sulfur tetrafluoride formation. After the iodine pentafluoride is consumed, continue stirring the reaction for 30min and then stop the reaction.

[0068] (4) Crude product gas detection: The reaction vessel temperature fluctuated between 23 and 29°C. Sulfur tetrafluoride was collected and collected after preliminary condensation (temperature 0 to 10°C). 181.3 kg of crude sulfur tetrafluoride was obtained. After external testing, the sulfur tetrafluoride content was 94.6%, and the yield was 93.9% based on the raw materials.

[0069] Example 5

[0070] This embodiment provides a method for preparing sulfur tetrafluoride at low temperature, the specific steps of which are as follows:

[0071] (1) Preparation of sulfur-containing solution: Weigh 57.4 kg of industrial sulfur (99%) and dissolve it in 132 kg of carbon disulfide. After dissolving, let it stand to separate into layers, remove the lower layer, filter to remove the insoluble matter in the upper layer, and obtain a mixed solution for later use.

[0072] (2) Purification of iodine pentafluoride: Iodine pentafluoride was distilled at 100.5℃, and 300 kg of the middle fraction with a content ≥99.5% was collected and bottled for later use;

[0073] (3) Continuous reaction: Add the mixture in (1) to a stainless steel reactor that has been purged with nitrogen and tested to be qualified (<80ppm). Maintain the reactor temperature at 25-30℃ and continuously introduce the iodine pentafluoride in (2) under micro-stirring (stirring speed 10-30r / min) to carry out the reaction. The rate of introducing iodine pentafluoride is adjusted by the change in the rate of sulfur tetrafluoride formation. After the iodine pentafluoride is consumed, continue stirring the reaction for 30min and then stop the reaction.

[0074] (4) Crude product gas detection: The reaction vessel temperature fluctuated between 23 and 29°C. Sulfur tetrafluoride was collected and collected after preliminary condensation (temperature 0 to 10°C). 174.7 kg of crude sulfur tetrafluoride was obtained. After external testing, the sulfur tetrafluoride content was 91.8%, and the yield was calculated to be 87.8% based on the raw materials.

[0075] Example 6

[0076] This embodiment provides a method for preparing sulfur tetrafluoride at low temperature, the specific steps of which are as follows:

[0077] (1) Preparation of sulfur-containing solution: Weigh 58.5 kg of industrial sulfur (99%) and dissolve it in 140.5 kg of carbon disulfide. After dissolving, let it stand to separate into layers, remove the lower layer, filter to remove the insoluble matter in the upper layer, and obtain a mixed solution for later use.

[0078] (2) Purification of iodine pentafluoride: Iodine pentafluoride was distilled at 100.5℃, and 300 kg of the middle fraction with a content ≥99.5% was collected and bottled for later use;

[0079] (3) Continuous reaction: Add the mixture in (1) to a stainless steel reactor that has been purged with nitrogen and tested to be qualified (<80ppm). Maintain the reactor temperature at 25-30℃ and continuously introduce the iodine pentafluoride in (2) under micro-stirring (stirring speed 10-30r / min) to carry out the reaction. The rate of introducing iodine pentafluoride is adjusted by the change in the rate of sulfur tetrafluoride formation. After the iodine pentafluoride is consumed, continue stirring the reaction for 30min and then stop the reaction.

[0080] (4) Crude product gas detection: The reaction process temperature fluctuates between 23 and 29°C. Sulfur tetrafluoride is collected and after preliminary condensation (temperature 0 to 10°C), 182.8 kg of crude sulfur tetrafluoride is obtained. After external testing, the sulfur tetrafluoride content is 96.9%, and the yield is 97.0% based on the raw materials.

[0081] Furthermore, the crude products obtained in the above embodiments were condensed at low temperature (-50 to -70°C) and tested with a fluorine analyzer, and the results showed that they did not contain fluorocarbon compounds.

[0082] In addition, the residues in the reaction vessels of each embodiment are centrifuged at low speed to remove most of the solid iodine, which can then be sold or recycled in the iodine pentafluoride synthesis process. The solution is then subjected to vacuum distillation, dust removal, condensation, and molecular sieve drying to obtain a reusable solvent.

[0083] Example 7

[0084] This embodiment provides a method for preparing sulfur tetrafluoride at low temperature. The only difference is that the mass ratio of sulfur to carbon disulfide is adjusted to 1:4; the other parts are basically the same as in Example 6. The specific steps are as follows:

[0085] (1) Preparation of sulfur-containing solution: Weigh 58.5 kg of industrial sulfur (99%) and dissolve it in 235 kg of carbon disulfide. After dissolving, let it stand to separate into layers, remove the lower layer, filter to remove the insoluble matter in the upper layer, and obtain a mixed solution for later use.

[0086] (2) Purification of iodine pentafluoride: Iodine pentafluoride was distilled at 100.5℃, and 300 kg of the middle fraction with a content ≥99.5% was collected and bottled for later use;

[0087] (3) Continuous reaction: Add the mixture in (1) to a stainless steel reactor that has been purged with nitrogen and tested to be qualified (<80ppm). Maintain the reactor temperature at 25-30℃ and continuously introduce the iodine pentafluoride in (2) under micro-stirring (stirring speed 10-30r / min) to carry out the reaction. The rate of introducing iodine pentafluoride is adjusted by the change in the rate of sulfur tetrafluoride formation. After the iodine pentafluoride is consumed, continue stirring the reaction for 30min and then stop the reaction.

[0088] (4) Crude product gas detection: The reaction process temperature fluctuates between 23 and 29°C. Sulfur tetrafluoride is collected and after preliminary condensation (temperature 0 to 10°C), 173.4 kg of crude sulfur tetrafluoride is obtained. After external testing, the sulfur tetrafluoride content is 85.6%, and the yield is 81.3% based on the raw materials.

[0089] Example 8

[0090] This embodiment provides a method for preparing sulfur tetrafluoride at low temperature. The only difference is that the molar ratio of iodine pentafluoride to sulfur is adjusted to 4:5. The other parts are basically the same as in Example 6. The specific steps are as follows:

[0091] (1) Preparation of sulfur-containing solution: Weigh 54.7 kg of industrial sulfur (99%) and dissolve it in 131.3 kg of carbon disulfide. After dissolving, let it stand to separate into layers, remove the lower layer, filter to remove the insoluble matter in the upper layer, and obtain a mixed solution for later use.

[0092] (2) Purification of iodine pentafluoride: Iodine pentafluoride was distilled at 100.5℃, and 300 kg of the middle fraction with a content ≥99.5% was collected and bottled for later use;

[0093] (3) Continuous reaction: Add the mixture in (1) to a stainless steel reactor that has been purged with nitrogen and tested to be qualified (<80ppm). Maintain the reactor temperature at 25-30℃ and continuously introduce the iodine pentafluoride in (2) under micro-stirring (stirring speed 10-30r / min) to carry out the reaction. The rate of introducing iodine pentafluoride is adjusted by the change in the rate of sulfur tetrafluoride formation. After the iodine pentafluoride is consumed, continue stirring the reaction for 30min and then stop the reaction.

[0094] (4) Crude product gas detection: The reaction process temperature fluctuates between 23 and 29°C. Sulfur tetrafluoride is collected and after preliminary condensation (temperature 0 to 10°C), 179.8 kg of crude sulfur tetrafluoride is obtained. After external testing, the sulfur tetrafluoride content is 90.6%, and the yield is 89.2% based on the raw materials.

[0095] Comparative Example

[0096] This comparative example provides a method for preparing a primary liquid sulfur tetrafluoride product with a purity ≥95%, the steps of which are as follows:

[0097] A. Fluorine purification: Fluorine gas is produced by electrolysis and then condensed at a temperature of -100℃ to remove a large amount of hydrogen fluoride gas from the fluorine gas, thus purifying the fluorine gas to 97%.

[0098] B. Preparation of iodine pentafluoride: Liquid iodine pentafluoride was prepared using fluorine gas purified in step A and refined iodine. The iodine pentafluoride was then purified with fluorine gas to obtain liquid iodine pentafluoride with a content of ≥99%. The reaction pressure was controlled at -0.098 MPa and the reaction temperature was controlled at 30℃.

[0099] C. Sulfur tetrafluoride reaction synthesis: Sulfur with an S content ≥99.5% is heated and melted, then reacted with liquid iodine pentafluoride with an IF5 content ≥99% prepared in step B in a sulfur tetrafluoride reactor to produce crude sulfur tetrafluoride gas, wherein:

[0100] The reaction equation is: 4IF5 + 5S = 5SF4 + 2I2

[0101] The excess amount of IF5 was controlled at 5%, the reaction pressure was controlled at 0.5 MPa, and the reaction temperature was controlled at 200℃.

[0102] D. Separation and Collection of Sulfur Tetrafluoride: The crude sulfur tetrafluoride gas synthesized by the reaction is cooled and condensed to solidify the iodine in the crude gas and liquefy the iodine pentafluoride. The liquid iodine pentafluoride flows back to the sulfur tetrafluoride reaction for recycling. The solid iodine is reacted with fluorine gas to produce liquid iodine pentafluoride, which flows back to the sulfur tetrafluoride reaction for recycling. The sulfur tetrafluoride in the separated mixed gas is condensed and collected, condensed into a liquid state, and separated from the impurity gas to obtain a primary sulfur tetrafluoride product with a purity of 95%. The cooling temperature is controlled at 10℃; the condensation separation temperature is controlled at -35℃; the condensation collection temperature is controlled at -100℃; and the temperature when fluorine gas is introduced is controlled at 30℃.

[0103] The comparative example has several problems, including extremely high difficulty and risk of fluorine purification; violent and uncontrollable reactions at high temperatures; and high energy consumption.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing sulfur tetrafluoride, characterized in that, include: Sulfur tetrafluoride is prepared by reacting iodine pentafluoride with sulfur dissolved in carbon disulfide at a temperature of 15-30℃. The mass ratio of sulfur to carbon disulfide is 1:1.5-3; The mass ratio of iodine pentafluoride to sulfur is 4:5.2-6.0; During the reaction, stirring is carried out at a speed of 10~30 r / min.

2. The method for preparing sulfur tetrafluoride according to claim 1, characterized in that, The sulfur has a sulfur content of ≥95% and a moisture content of less than 100ppm; the carbon disulfide has a purity of ≥99%.

3. The method for preparing sulfur tetrafluoride according to claim 1, characterized in that, The iodine pentafluoride has a purity of ≥99.5% and is obtained by distillation.

4. The method for preparing sulfur tetrafluoride according to claim 3, characterized in that, The distillation temperature is 100-104.5℃.

5. The method for preparing sulfur tetrafluoride according to any one of claims 1-4, characterized in that, After the reaction is complete, the crude gas obtained is collected after preliminary condensation and impurity removal.

6. The method for preparing sulfur tetrafluoride according to claim 5, characterized in that, The condensation temperature is 0-10℃.

7. The method for preparing sulfur tetrafluoride according to claim 6, characterized in that, An inert gas protection system is in place throughout the reaction process.

8. The method for preparing sulfur tetrafluoride according to claim 7, characterized in that, The inert gas is nitrogen.

9. The method for preparing sulfur tetrafluoride according to claim 1, characterized in that, The method includes the following steps: S1. Add sulfur to a stainless steel stirred tank, pump in carbon disulfide solution and stir to dissolve, separate the liquid to remove water, take the lower layer solution, filter and pump it into a solvent tank for later use. Iodine pentafluoride was purified by distillation and then stored in a steel cylinder for later use. S2. Add carbon disulfide containing sulfur dissolved in S1 to the stainless steel reactor after nitrogen purging, and keep the reactor at a constant temperature by circulating cold water. S3. Slowly and continuously add purified iodine pentafluoride to the reactor and stir the reaction. S4. The crude gas obtained from the reaction is collected after preliminary condensation to remove impurities.

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